New York, New York - President Joe Biden was joined in New York on Thursday by his predecessors Barack Obama and Bill Clinton at a blockbuster fundraising event where he collected $25 million to go towards his re-election bid.

The Democrat's bumper evening took place at Radio City Music Hall in Manhattan, around an hour's drive from where his Republican rival Donald Trump had earlier attended a wake for a New York police officer killed on duty.

Biden's campaign team announced ahead of the event a "record" collection of more than $25 million, noting it was more than Trump had raised for the whole of February.

But as the 81-year-old raked in financial support ahead of November's election, pro-Palestinian demonstrators protested outside the venue, and several inside the hall whistled and shouted before being ushered away.

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Biden's unconditional support for Israel's brutal war on Palestinians in Gaza, where over 32,000 people have been killed in less than six months, has roiled his base, with hundreds of thousands of voters threatening to abandon him come November.

Thursday's event had a celebrity tinge.

Singers Queen Latifah, and Lizzo, among others, warmed up the room before the 42nd, 44th and 46th presidents of the United States sat down for a question-and-answer session moderated by Stephen Colbert. Vogue editor-in-chief Anna Wintour was also in attendance.

The discussion mixed serious topics with jokes, and ended when Obama and Clinton joined Biden in donning aviator sunglasses, Biden's favorite accessory.

Trump's campaign spokesperson, Steven Cheung, had blasted on X the "glitzy fundraiser... with their elitist, out-of-touch celebrity benefactors."

According to NBC News, guests at the event could pay $100,000 for a photo with the trio.