There are at least 750 suspected Ebola cases in the DRC, along with 177 suspected deaths, Tedros Adhanom Ghebreyesus said.
He said 72 cases and seven deaths have been confirmed, but the number of suspected cases and deaths was much higher.
"These numbers are changing as surveillance efforts and laboratory testing is improving, but violence and insecurity are impeding the response," Mr Ghebreyesus said.
Mr Ghebreyesus said the outbreak in the DRC was "spreading rapidly" and now poses a "very high" risk at the national level.
The UN health agency was revising its assessment of the risk within the country from high to "very high", he said. The risk remains high for regional spread and low at global levels, he added.
Additional WHO personnel have been deployed to Ituri, the epicentre of the outbreak, he added.
In neighbouring Uganda, two cases and one death have been confirmed.
University of Oxford scientists working on vaccine
It comes as scientists from the University of Oxford are working to develop a new vaccine which could be used to combat the outbreak.
Professor Teresa Lambe OBE, the head of vaccine immunology at the Oxford Vaccine Group and Pandemic Sciences Institute, said: "My hope is that this outbreak can be brought under control quickly and that vaccines are ultimately not needed.
"Nevertheless, our team and partners will continue working to ensure that potential vaccine options are available if they are needed."
The WHO said the vaccine could be available for use in clinical trials in two to three months, the BBC reported.
Treatment centre set alight
Mr Ghebreyesus's comments about "violence and insecurity" come after a treatment centre was set alight by an angry crowd.
Clashes broke out in the town of Rwampara, in Ituri, on Thursday after the family of an Ebola victim disputed the disease had killed him and demanded his body be handed over to them.
Witnesses told the Reuters news agency that protesters gathered outside the hospital and set fire to tents run by a medical charity, prompting police to fire warning shots and tear gas.
Bodies of Ebola victims are highly infectious after death, and unsafe burials are a leading cause of transmission.
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On Thursday, a case was confirmed in the DRC, hundreds of miles from the epicentre, in a rebel-held area of the country, signalling a further spread of the disease.
The Bundibugyo strain responsible for the outbreak has no approved vaccine or treatment, and the WHO has declared a public health emergency of international concern.
On Thursday, Britain said it was allocating up to £20m to the response, through support for frontline health workers, improved infection control and disease surveillance.
The US has so far committed £17.1m ($23m) and said it would help open up to 50 clinics in DRC and Uganda.
The world-famous aerobatic team will perform with a full "Diamond Nine" on special occasions such as to mark the King's birthday and as part of an international flypast in the US on 4 July to commemorate the 250th anniversary of Independence Day.
However, only seven jets will dazzle the crowds with their aerial stunts during the first display of the season this weekend in Crete and for much of the rest of the summer.
The engine that powers the ageing Red Arrows Hawk T1 jet is no longer in production.
It means the Royal Air Force Aerobatic Team need to rotate the use of their remaining engines, which can be swapped in and out of aircraft in the same way as engines are moved in and out of Formula 1 cars.
The reduced formation will continue to be the norm until the Ministry of Defence buys a replacement Red Arrows fleet.
But this decision has been impacted by a delay in the release of a major plan for new investment in the army, navy and air force.
The defence investment plan should have been published last autumn.
It's still under wraps.
An aerospace company that had been vying for the Red Arrows contract even went into administration during the wait.
The incumbent Hawk aircraft are finally due to be retired in 2030.
The previous Conservative government had extended their out of service date in 2021.
The older the airframe and engine, the more time is required for maintenance and safety checks to ensure it remains airworthy.
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A spokesperson for the Royal Air Force said: "The Red Arrows will fly in a nine aircraft formation for HM The King's Birthday Flypast and the 4th of July 250 Commemorations in the USA this year.
"For other displays, they will operate with a seven aircraft, continuing to deliver high‑quality engaging displays at air shows and events across the UK, mainland Europe and further afield.
"This will support the sustainable management of the Hawk T1 fleet and prepare the team for a transition to a future aircraft type."
A decision was taken by air chiefs earlier in the year to reduce the Red Arrows team to seven aircraft from nine to ease the pressure on the engines.
It is not the first time the squadron has flown with a shrunken formation.
In 2022, the Red Arrows again operated with just seven aircraft following claims of a "toxic culture" that ultimately resulted in two pilots being sacked.
Sky News published a documentary in December 2024 that featured interviews with three women and one man, all former members of the squadron, who said they experienced sexual harassment, sleaze and bullying in a scandal that triggered an RAF inquiry.
The England manager only had 26 places to offer for the tournament, which starts on 11 June, when Mexico face South Africa.
Tough decisions were expected, but some of Tuchel's choices have still been met with surprise.
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In goal, Newcastle United's Nick Pope misses out. Brighton and Hove Albion's Jason Steele will be coming along as a training goalkeeper, but would not be expected to play in the tournament.
Pope, 34, has earned multiple caps for England before but failed to catch Tuchel's eye this season.
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Another notable defensive miss is Harry Maguire, one of the most high-profile omissions.
The 33-year-old said on social media that he was dismayed, writing: "I was confident I could [have] played a major part this summer for my country after the season I've had. I've been left shocked and gutted by the decision.
"I've loved nothing more than putting that shirt on and representing my country over the years. I wish the players all the best this summer."
His teammate Luke Shaw, 30, has been a regular for England at recent tournaments but has also been overlooked in favour of Manchester City's Nico O'Reilly, 21.
Other defenders who failed to make the cut were Chelsea's Levi Colwill, 23, who has struggled with injury this season, and Real Madrid's Trent Alexander-Arnold, 27, one of England's biggest stars.
Many felt Alexander-Arnold offered a valuable creative outlet, but it seems Tuchel has been unimpressed with his start to life in Spain.
Possibly the biggest surprise, however, was the omission of Chelsea's Cole Palmer. The 24-year-old scored during England's defeat to Spain in the Euro 2024 final. But he faced stiff competition in his position.
Another attacking midfielder who missed out was Nottingham Forest star Morgan Gibbs-White, 26, but it appears Tuchel felt Real Madrid star Jude Bellingham, 22, and Aston Villa's Morgan Rogers, 23, offered him a sufficient threat instead.
Another significant name to miss out is Manchester City's Phil Foden, 25, despite Tuchel's experimentation with him in recent friendlies.
Meanwhile, the inclusion of Manchester United's Kobbie Mainoo, 21, appears to have cost Adam Wharton his place after the Crystal Palace midfielder was left out.
Competition was also too fierce for West Ham United forward Jarrod Bowen, 29, whose side face relegation from the Premier League to the Championship on Sunday unless they beat Leeds United - and Tottenham Hotspur lose to Everton FC.
Tuchel praised Bowen for his attitude, but said he favoured Noni Madueke, 24, whose Arsenal side were recently crowned Premier League champions.
Other omissions of note include Newcastle United's Lewis Hall, 21, Everton's James Garner, 25, and Leeds United striker Dominic Calvert-Lewin, 29.
Arsenal's Myles Lewis-Skelly, 19, and Brighton forward Danny Welbeck, 35, also miss out.
Chalmers, who was 90, died on Thursday evening. Her family said she had become seriously ill in recent weeks.
In a statement to Sky News, they said she died peacefully at home, surrounded by her family, after living with Alzheimer's in her final years.
Chalmers' family said: "After living an extraordinary life that involved over 60 years in broadcasting and countless adventures all over the globe, Judy sadly passed away last night, surrounded by the family she loved so much after suffering with Alzheimer's for some years.
"We will miss her greatly but she leaves behind a giant suitcase of the happiest of memories."
Fans paid tribute on social media, with one calling her "a national treasure".
Chalmers, who was born in Gatley, Cheshire, started working for the BBC when she was just 13.
In the 1960s, she presented two BBC radio programmes, Family Favourites and Woman's Hour.
She also presented the BBC's Come Dancing from 1961 to 1965.
In 1974, Chalmers started presenting ITV's travel programme Wish You Were Here...? - a gig she kept until 2003.
In the 1980s, she was a regular host of the Miss World contest on ITV, as well as the BBC's Children's Television Club which later became Blue Peter.
In 1994, she was made an Officer of the Order of the British Empire (OBE) for her services to broadcasting.
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In 2008, her son, Mark Durden-Smith, hosted a new version of the show, called Wish You Were Here...? Now & Then, which saw locations from the show's original series revisited to see how they had changed.
She leaves behind her husband, former sports commentator Neil Durden-Smith, their two children, and six grandchildren.
The EA says it has released the list to provide the public with better information about what sites it's investigating and improve intelligence gathering.
Some 13 of the 117 sites listed are in Kent, with eight in West Sussex and seven in Norfolk. East Sussex is home to six, and there are five each in Buckinghamshire and Surrey.
The sites have several different types of waste, including household, construction and commercial waste.
Sky has previously investigated mega dumps, including a 100,000-tonne dump near Epping in Essex, and in Bolton House Road in Wigan.
The EA has said all sites on the list will be reviewed every month.
The agency's chief executive Philip Duffy said: "Publishing this watchlist is a deliberate act of transparency - communities need to know that we are acting, and we want those committing these crimes to know that we are coming for them."
"We are using every tool at our disposal to find those responsible and encourage anyone with information to come forward," he added.
Details about the exact locations of some sites are restricted due to ongoing police and EA investigations.
Last week, Sky News revealed the existence of three new mega dumps being investigated by the Environment Agency - collectively weighing in at more than 120,000 tonnes.
The sites are in Ranskill in Nottinghamshire, Faversham in Kent, and Bracknell in Berkshire.
In a letter seen by Sky News from the EA to the House of Lords Environment and Climate Change Committee, the agency's chief executive Philip Duffy said there are a total of 537 illegal waste sites in the UK.
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This figure includes 28 mega dumps that are larger than 20,000 tonnes.
The EA's decision to identify the locations of 117 sites comes after it announced its 10-point plan to tackle waste crime in March.
More intelligence gathering, a more consistent and quicker response to dumping reports, and naming and shaming operators involved are amongst the measures to tackle the organised crime gangs behind the dumps.