LONDON—A rare Western fundraiser held in support of pro-Russian rebel areas in eastern Ukraine was interrupted on Thursday night when things got physical between the main speaker and a member of the crowd.

Graham Phillips, a star of the Kremlin-funded TV network RT during the rebellion, rushed offstage to confront a heckler in London who claimed pro-Russian forces in Ukraine were terrorists. The heckler later filed a complaint to police officers alleging that he had been assaulted.

After a week in which at least two venues had canceled Phillips’s event, he was in no mood to apologize. “I shoved him,” he told The Daily Beast. “If he’d hit me, I would have definitely put one on his chin.”

The sound of a resounding slap, followed by a gasp from Phillips’s supporters, suggested there may have been some physical contact between the men. The man on the receiving end, Will, 33, claimed that he had been struck on the back of the neck.

Will, who asked that his last name be withheld for fear of reprisals, said he had chosen to attend the auction in order to confront Phillips and raise questions over the legitimacy of his fundraising. He bought one of the photographs in the auction in order to track where the money will be sent.

Phillips, whose YouTube reports from the front lines have won millions of views, said the profits from the auction would be used to fund a hospital in Donbass, an area of eastern Ukraine now under pro-Russian rebels’ control. He opened the event by telling the crowd of about 70 people that he wanted “this event to be a positive thing.”

Seconds later, a contretemps overtook the small restaurant in Finsbury Park. Phillips had just introduced his photographs, which were to be auctioned off later in the evening. The heckler, Will, took exception to a flattering portrait of “Givi,” one of the pro-Russian rebel leaders, whom he accused of war crimes.

“Givi is a murderer!” Will shouted.

Phillips stepped down from the tiny stage. “Come and say that to my face,” he said. “You’re a scumbag.”

He raced over to Will and shoved him toward the exit as the crowd, made up mostly of Russian expats, chanted “out, out.” A police officer confirmed that an assault allegation had been filed to Scotland Yard.

The photo that started the fight, which Phillips signed onstage, was ultimately bought by a young Russian businessman, Philip Bobrov, for about $225. Bobrov, 22, who moved to Britain four years ago, said the truth about Vladimir Putin’s actions in Ukraine was complex, “but I think the people of Donbass need our help.”

Critics say Phillips rarely allows for complexity in his reporting, which appeared regularly on RT until he fell out with the Kremlin-backed station over a video in which he claimed to have been shot at.

“The journalist’s previous record of reporting for RT has already backfired on him,” the channel told BuzzFeed last year.

Phillips still describes himself as a journalist or a Donbass correspondent, despite his seemingly one-sided approach. “I am objective, but I would say my side is what I’ve seen there,” he told The Daily Beast, although he struggled to avoid the first person plural when describing the pro-Russian rebels.

“I feel like we’re together and I feel that doesn’t obfuscate my reporting, but I do feel a bond, a kinship, with these people of Donbass,” he said. “This charity event might blur the line of the journalist, but I think within the scope of a journalist you can do some good.”

He went on to claim that the passenger plane MH17 was shot down by the Ukrainian government, not pro-Russian forces.

Despite his entrenched criticism of the British government and what he describes as its pro-Ukraine “propaganda,” Phillips denied that he is an heir to the notorious Cambridge spy ring that worked for the KGB. “I’m completely opposed to the Anthony Blunts and Kim Philbys; all these people put the interests of another country before their own; they’re just traitors,” he said. “I think I’m the opposite, I’m correctly representing the position Great Britain should be, instead of the malinformed position the government has taken under the malaise of the European Union and overwhelming weight of the Western world perpetuating this propaganda that emanates from the U.S.”

The reporter, who said his journalism training began during an internship at the Guardian, pledged to hold Donbass fundraisers regularly in London. In the meantime, he will return to Russia and eastern Ukraine, where his critics are likely to remain silent.