A 26-year-old man is in an induced coma at Westmead Hospital after a violent brawl broke out at a fundraiser event in Lidcombe in Sydney's West.

The fight, which involved more than 100 people, started near the community centre around midnight and moved onto Lidcombe's Bridge Street.

The riot squad was called in to break up the crowd, which had gathered for a Tonga tsunami recovery fundraiser.

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Police say bottles, fists and logs were used as weapons.

"When police arrived at the scene it was quite chaotic," Detective Inspector Karl Leis, said.

"There were a number of people who had engaged in fights at the scene.

"We're not suggesting all the people there were involved in a melee."

Police, who said they were unaware of the large fundraiser, issued a warning.

"We have a situation now where a 26-year-old is in a critical condition in hospital," Inspector Leis, said.

"If people are heading out for a night, take personal responsibility because there can be life-changing consequences."

A 22-year-old Regents Park man with an outstanding warrant was arrested and refused bail, while a 31-year-old was fined for offensive conduct.

Investigations are ongoing.