A red Seat Leon collided with a Citroen C4 Picasso in Wigan Road, Bolton in the early hours 11 January, Greater Manchester Police (GMP) said.
The driver of the Seat and two passengers, all believed to be men aged between 18 and 19, were named locally by the Bolton Council of Mosques (BCoM) as Mohammed Jibrael Mukhtar, Farhan Patel and Muhammad Danyaal Asghar Ali.
Mosrab Ali was also named locally and is believed to be the taxi driver, who police said is aged in his 50s.
All were declared dead at the scene, while five injured passengers were taken to hospital, the force said.
GMP Chief Inspector Helen McCormick earlier said formal identification was taking place and the families of those thought to be involved had been informed and were being supported by specialist family liaison officers.
Chief Inspector McCormick called the incident "devastating", adding that the crash scene was "particularly challenging" for the emergency services.
Footage from a nearby property shared online showed a head-on crash, before both cars and debris were sent flying in different directions.
A spokesperson for Greater Manchester Fire and Rescue Service said: "At around 12.50am this morning, three fire engines and the technical response unit attended a crash involving a taxi and a car on Wigan Road, Bolton.
"Firefighters arrived quickly to make the area safe and used cutting equipment to help remove people from the vehicles before passing them into the care of North West Ambulance Service.
"Greater Manchester Police assisted with cordoning the area. Crews were in attendance for roughly two hours."
A local woman said she was woken by a "loud bang" and saw "quite a bit of debris" on the road, along with a red car that was "really damaged".
Councillor Ayyub Patel, of Bolton Council, told Sky News the "incredibly tragic incident" had left the whole community "devastated".
He offered his "heartfelt condolences" to the families and loved ones affected.
Residents "will need time to process and recover from such a profound loss", he said, as he asked people to "avoid speculation and allow the investigation to take its proper course".
A statement from BCoM said: "BCOM is very sad to announce that there was a tragic accident early hours in the morning and the subsequent loss of four young lives.
"BCoM is closely supporting the families and liaising with the relevant authorities. The authorities are professionally, expediently and empathetically dealing with all the necessary issues.
"It is anticipated that details of the burial will be announced as soon as possible. Please make dua for the deceased and their families and allow them privacy."
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GMP's Serious Collision Investigation Unit (SICU) is urging any witnesses to come forward with information, including if they have any dashcam or CCTV footage of the incident.
A scene is in place as the investigation continues, GMP said.
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Details on the protests are scarce as a communications blackout is still in effect across Iran's 31 provinces, with demonstrations, which began at the end of December over a sharp decline in the value of the rial currency, continuing into their third week.
They have since transformed into the most significant challenge to the regime for several years.
Over the weekend, Tehran's prosecutor-general said those demonstrating will be tried as "enemies of god" - a charge punishable by the death penalty - and Donald Trump said the US is "ready to help" protesters.
Meanwhile, US foreign secretary Marco Rubio has discussed the situation - and the possibility of American intervention - with Israeli Prime Minister Benjamin Netanyahu.
Read more: Body bags show emerging picture of Iranian crackdown
According to the US-based Human Rights Activists News Agency, at least 544 people have now been killed during the disorder - up from 116 deaths recorded by the end of Saturday.
It added that it has also received 579 other reports of deaths that remain under investigation, which would bring the total to 1,123.
More than 10,681 individuals have also been transferred to prisons following arrest, the non-government organisation said.
It added in an update earlier on Sunday that most of the victims were killed by live ammunition or pellet gunfire, predominantly from close range.
State TV showed dozens of body bags on the ground at the coroner's office in Tehran, saying the dead were victims of events caused by "armed terrorists", as well as footage of people gathered outside the Kahrizak Forensic Medical Centre in the capital waiting to identify bodies.
Iranian president ready to listen to people
It comes after Iran's president, Masoud Pezeshkian, addressed the protests for the first time in an interview with regime-linked national media.
During the interview, he said "terrorists" linked to foreign powers were killing people, burning mosques and attacking public property, and that Iran's enemies were looking to "sow chaos and disorder" by "ordering riots".
However, Mr Pezeshkian said the Iranian establishment was ready to listen to its people, and that the government was determined to resolve people's economic problems.
He then urged citizens to distance themselves from "rioters and terrorists," who he said were trying to "destroy the entire society".
Speaker: US strikes would make bases 'legitimate targets'
Meanwhile, Mohammad Baqer Qalibaf, the speaker of the Iranian parliament, suggested the regime would retaliate against any US attack.
It followed Mr Trump's remarks on Friday that the US would hit Tehran "very hard" if the government "start[s] killing people", which the speaker said would make Israeli and regional US bases "legitimate targets".
While Mr Qalibaf was speaking, MPs in parliament shouted "Death to America!"
Citing an Israeli source, the Reuters news agency reported that Mr Netanyahu and Mr Rubio did discuss the possibility of a US intervention in Iran in a phone call on Saturday.
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Israel is now on high alert for a possible US intervention in Iran amid ongoing anti-government protests, three Israeli sources also told the news agency.
A US official confirmed only that the conversation took place, not its content.
Separately, the Israeli prime minister praised the "demonstrations for freedom," adding: "The people of Israel, and indeed the entire world, marvel at the immense bravery of the citizens of Iran.
"We all hope that the Persian nation will soon be freed from the yoke of tyranny."
Several videos centre around a forensics institute in the neighbourhood of Kahrizak, south of the capital, Tehran.
Some have been filtered out via Starlink, but Iranian state TV has footage from the same location.
Latest updates on Iran protests
All show a multitude of body bags, some lined up on the floor or on mortuary trolleys, others in long rows outside as relatives search for loved ones.
One video contains telling information.
It films a screen inside the forensics centre which identifies the dead through a long list of photos, as a loudspeaker calls out their names and asks relatives to collect the body.
On the left of the screen is a long list of jpeg numbers, correlating with the photos of the deceased. There are 250 of them.
The date on the screen is 9 January, Friday.
This suggests that in this morgue alone there are the bodies of 250 people, killed during Thursday night's protests.
Secret burial
Twenty-three-year-old Robina Aminian was shot in the head that night.
She was studying fashion at university in Tehran and had gone to join the protests after class.
Two family members told Sky News how authorities tried to prevent them from retrieving her body.
They finally managed to take her to Kermanshah in western Iran, where they gave her a secret burial.
From their reports, it would appear the regime wants to avoid the spectacle and momentum which large-scale mourning might give to the protests, as it did during the revolution which brought the ayatollahs to power in Iran in 1979.
"The Iranian tradition of funeral is that when somebody dies, on the 40th day of the passing of the deceased, people gather to commemorate the death," says Sina Azodi of the Atlantic Council.
"In 1978, the revolution and the 40-day ceremony mobilised people to chant against the shah's regime, and then there were more people killed during those demonstrations so there was a cycle, creating martyrs for the revolution.
"The Islamic Republic has learned that lesson."
Read more:
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Everything you need to know about the protests
The scant information filtering out of Iran makes an already murky situation even more difficult to understand.
The US president promised retaliation if the Iranians started firing on protestors, and now he will be weighing his options.
One further point of comparison with these protests and the revolution which unseated the shah is that then, as the system started to crumble, the security forces knew the West would welcome them with open arms.
That is very far from being the case now.
Which means the probability the Revolutionary Guard hunkers down, staying loyal to the hand which feeds them, that bit more likely - a dangerous proposition for the protesters on Iran's streets.
The man, thought to be aged in his 50s, had been skiing off-piste in La Plagne, according to the resort.
It said in a statement that at 1.57pm on Sunday, rescue teams got an avalanche alert and went to the site in southeastern France.
A team of around 52 people, including medics and ski school instructors, as well as a helicopter-deployed piste dog, were called in.
The Englishman was discovered after 50 minutes of searching under 2.5m of snow, the resort said.
He was with a group when the avalanche struck, but was not equipped with an avalanche transceiver and was not with a professional instructor, it added.
La Plagne said its thoughts were with the man's family.
NATS has apologised for the disruption and said the outage was caused by poor weather in the area. They added that their engineers were working with National Grid to resolve the issue as quickly as possible.
Nine flights have been cancelled or diverted at the airport, with at least 12 due to be delayed - several flights have delays of over four hours.
A spokesperson said: "Due to a technical issue with NATS' radar that serves Birmingham Airport, only departing flights are currently operating, with some delays.
"All arriving flights are currently suspended. We apologise for the delay to customers, and we are working closely with NATS to rectify the issue."
Multiple flights have been diverted to East Midlands Airport and Liverpool's John Lennon Airport.
Previous incidents
This isn't the first time a power issue has caused problems for a major UK airport.
Last March, a power outage shut Heathrow Airport, causing travel chaos for more than 270,000 passengers.
A report found that the incident, which led to the cancellation of around 1,300 flights, was caused by a "catastrophic failure" of equipment in a nearby substation.
NATS also came under fire last year, particularly from airlines, when air traffic problems resulted in more than 1,000 flights departing UK airports being cancelled.
Martin Rolfe, the chief executive of NATS, told Sky News an initial investigation found the air traffic control failure was caused by flight data which its system "didn't understand" and "couldn't interpret".