An organised street fight involving up to 40 people armed with knives, machetes, and baseball bats in Sydney’s west has left a man fighting for life.

Police were called to a reserve on Byrnes Street in South Granville about 5.40pm yesterday following reports of the brawl.

When police arrived the group fled on foot and in cars.

Officers found a 28-year-old man with serious head injuries.

He was taken to hospital in a critical condition.

Superintendent Simon Glasser said the man’s chances were “touch and go”.

“Hopefully he pulls through,” he said.

“We do believe it was a pre-arranged meeting that went out of control.”

Witnesses have told 9News the 28-year-old man was trying to stand up for a 15-year-old boy being bullied when he was allegedly set upon by the group.

A 29-year-old man was arrested in Mons Street, South Granville, and charged with affray and carrying a knife in public.

He was refused bail and will front Parramatta Local Court tomorrow.

Police are urging others involved to come forward.