Officers were called to a report of an assault outside MyBar in Charminster Road at about 3am on Monday.
A man in his 40s, from Christchurch, was pronounced dead at the scene.
Dorset Police said two men, aged 37 and 46, from Bournemouth and a 34-year-old man from Poole have been arrested.
Detective Chief Inspector Nicky Jenkins said: "Our thoughts are with the family of the man who sadly died and a detailed investigation is under way to establish what happened.
"An extensive cordon has been put in place and I would like to thank the public for their understanding while vital work at the scene is carried out."
The officer added: "We know there were a number of people in the area at the time who may have witnessed what happened and we would ask them to please get in touch.
"I am also appealing to anyone who was driving in the area and has dashcam fitted to their vehicle to please check it for any relevant footage."
Anyone with information is asked to contact Dorset Police.
The child, believed to be named Kim Ju Ae and aged around 13, has accompanied her father to several high-profile events since late 2022.
And the pair rode in a tank together last month, sparking further speculation she is being positioned as the North's future leader.
On Monday, South Korea's National Intelligence Service (NIS) director Lee Jong-seok said in a closed-door briefing at the National Assembly the girl could be considered Mr Kim's successor, according to Lee Seong Kweun, one of the politicians in attendance.
NIS said its assessment was based on "credible intelligence" collected by the agency.
Asked about potential protests from Mr Kim's sister Kim Yo Jong, who has been long regarded as North Korea's number two figure, the NIS director responded that she has no substantial powers, Mr Lee told a briefing.
It is the agency's strongest assessment yet on the rising political status of the teenager who it believes could extend her family's rule into a fourth generation.
In early 2024, the NIS described the child as Mr Kim's likely heir, and in February this year, the agency said it believed she was close to being designated as the nation's future leader.
Some observers disagree with the assessments, arguing North Korea's extremely male-dominated society won't likely embrace a woman leader.
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They also say Mr Kim, 42, is too young to name a future leader, a development that could weaken his ruling of the country.
In a public appearance in March, the pair fired pistols during a visit to a light munitions factory.
The NIS, during Monday's briefing, said North Korean authorities appeared to have organised such events to build up her military credentials and "reduce scepticism about a woman successor", Mr Lee said.
The girl's reported name is based on an account by former NBA star Dennis Rodman, who recalled holding Mr Kim's baby daughter during a visit to Pyongyang in 2013.
North Korea, established in 1948, has been successively ruled by male members of the Kim family.
Kim Jong Un inherited power upon his father Kim Jong Il's death in late 2011. Kim Jong Il took control after his father and state founder Kim Il Sung died in 1994.
John Miller, 48, was last seen on 10 November 2025.
He was reported missing from the Cumbernauld area.
In an update on Monday, Police Scotland said it received a report of a body being found in woods near to Hillcrest Terrace in the North Lanarkshire town at about 4.25pm on Sunday.
While formal identification is yet to take place, Mr Miller's family has been informed.
The force added: "The death is being treated as unexplained but there does not appear to be any suspicious circumstances."
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A report will be submitted to the procurator fiscal in due course.
West has previously been condemned over his antisemitic remarks.
The 48-year-old US rapper - who has not performed in the UK since he headlined Glastonbury in 2015 - is set to top the bill for all three nights of the festival in London's Finsbury Park in July.
Festival organisers - and the government - are now coming under increasing pressure over the booking.
A Pepsi spokesperson said: "Pepsi has decided to withdraw its sponsorship of Wireless Festival."
Diageo, owner of Johnnie Walker and Captain Morgan, said on Sunday evening it had also withdrawn.
A spokesperson said: "We have informed the organisers of our concerns and as it stands, Diageo will not sponsor the 2026 Wireless festival."
PayPal, which is a payment partner for the festival, will not appear in any future promotional materials, Sky News understands.
Festival organisers have been contacted for a response.
In the time since he last performed on UK soil, West has drawn criticism for antisemitic X posts, a Super Bowl advert directing people to a swastika T-shirt and a song referencing Hitler.
Sir Keir said it was "deeply concerning" that West has been booked "despite his previous antisemitic remarks and celebration of Nazism".
"Antisemitism in any form is abhorrent and must be confronted clearly and firmly wherever it appears. Everyone has a responsibility to ensure Britain is a place where Jewish people feel safe and secure," the prime minister said.
West, also known as Ye, has been barred from X over antisemitism on multiple occasions.
In January, West took out a full-page advert in the Wall Street Journal to apologise, titled: "To Those I've Hurt."
"I am not a Nazi or an antisemite," it said. "I love Jewish people."
West attributed his previous outbursts to his bipolar-1 disorder, writing: "In early 2025, I fell into a four-month-long manic episode of psychotic, paranoid and impulsive behaviour that destroyed my life.
"I lost touch with reality. Things got worse the longer I ignored the problem. I said and did things I deeply regret."
The rapper also apologised to the black community, saying he had let it down.
West previously lost his deal with Adidas following a post on his social media in 2022, in which he shared an image of a swastika inside a Star of David.
Adidas, which had worked with the rapper on his Yeezy trainers, subsequently donated more than $150m (£117m) to anti-hate groups.
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Shortly afterwards, he drew criticism over a TV advert that directed people to a website selling a swastika t-shirt and released a song titled Heil Hitler.
Sir Ed Davey, the leader of the Liberal Democrats, last week called for the government to ban West from entering the UK.
He said Home Secretary Shabana Mahmood should "ban him from coming to this country - we've got to take antisemitism more seriously".
On Monday, shadow home secretary Chris Philp echoed his calls in a letter to Ms Mahmood, calling for her to use immigration laws to prevent West from entering the UK.
He described West's previous comments as "not a one-off lapse, but a pattern of behaviour that has caused real offence and distress to Jewish communities", and added: "At a time when antisemitism is rising in the UK, allowing someone with his track record to headline a major public event sends entirely the wrong message."
In a post on X, the Campaign Against Antisemitism (CAA) backed banning West from entering the UK.
It said: "The government can ban anyone from entering the UK who is not a citizen and whose presence would 'not be conducive to the public good'.
"Surely this is a clear case."
Sky News understands the Home Office is yet to receive an application for West to enter the UK.
Nancy Guthrie, 84, was last seen at her Arizona home on 31 January and was reported missing the following day.
Officials say her blood was found on the front porch. Purported ransom notes were sent to news outlets, but deadlines for paying have passed.
Authorities believe she was kidnapped or abducted. During the investigation, the FBI released surveillance videos showing a masked man on the porch that night.
Today co-anchor Ms Guthrie, 54, has acknowledged she's a changed person since her mother's disappearance and that it's difficult to press ahead without knowing what happened to her.
Despite a search that involved thousands of federal and local officers and volunteers, there has been no sign of the mother-of-three since she went missing.
In a video message released by her New York church on Easter Sunday, Ms Guthrie said she felt "moments of deep disappointment with God, the feeling of utter abandonment".
But she said the resurrection is not fully celebrated "if we do not acknowledge the feelings of loss, pain, and yes, death".
"Perhaps this is too dark a message to share on Easter morning, but I have long believed that we miss out on fully celebrating resurrection if we do not acknowledge the feelings of loss, pain and, yes, death," she said.
"It is the darkness that makes this morning's light so magnificent, so blindingly beautiful."
In her closing message, she said: "I see a bright vision of the day when heaven and Earth pass away because they are one, on Earth as it is in heaven.
"When we celebrate today, this is what we celebrate, and I celebrate, too. I still believe. And so I say with conviction, 'Happy Easter.'"
Announcing her return to NBC's flagship morning show, Ms Guthrie said she was unsure whether she'll feel like she still belongs.
"It's hard to imagine doing it because it's such a place of joy and lightness," she said just over a week ago on Today in her first interview since her mother's disappearance.
"I can't come back and try to be something that I'm not. But I can't not come back because it's my family."
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Ms Guthrie, one of US morning television's most recognisable faces, has been a co-anchor on Today since 2012.
There had been a great deal of speculation about whether she would return to the show.
"I want to smile, and when I do it will be real," she told broadcaster Hoda Kotb, who returned to Today to fill in for Ms Guthrie while she concentrated on the search.
"Being there is joyful, and when it's not I'll say so."
Nancy Guthrie made occasional appearances on Today over the years, once taking part in a cooking demonstration and surprising her daughter on set.
When Savannah Guthrie returned to her hometown of Tucson last year for a segment recorded for the show, the pair attended one of their favourite restaurants and talked about their love of Arizona.
The Guthrie family has offered a $1m (£754,000) reward for information leading to the return of their mother.
The FBI and the Pima County Sheriff's Department both said late last week that they had no updates.
Early on, some media outlets reported receiving ransom messages linked to the case.
Ms Guthrie said she and her siblings responded to two they believed to be real and offered to pay.
Ms Guthrie said her celebrity status might be the reason her mother was taken, but that possibility was "too much to bear".