A mass brawl at a shopping centre involving 'hammers and a knife' has left a number of teenagers in hospital with one undergoing surgery.

On Monday evening a group of six teenagers left a restaurant at Rhodes Shopping Centre in Sydney's inner-west when they were approached by two other groups of youths.

Police said it appeared that they had been waiting for the teenagers while they were inside the eatery and ambushed them once they emerged.

A mass brawl at Rhodes shopping centre in Sydney's inner-west broke out on Monday evening

Witnesses told the Sydney Morning Herald the groups were armed with hammers, and at least one had a knife.

An 18-year-old suffered a stab wound to his abdomen and a cut to his ear, and was rushed to Westmead Hospital.

He underwent surgery overnight and is now in a stable condition.

Another man, also aged 18, suffered a neck injury during the brawl and was taken to Concord Hospital in a stable condition.

One man, 18, was stabbed in the abdomen while another, also 18, suffered neck injuries (pictured is one of the injured men)

A female, 16, was treated at the scene for a cut to her hand.

Police have seized CCTV footage of the brawl in an attempt to identify those involved in the ambush.

The motivation for the attack is unknown, and no property was stolen. No arrests have been made at this stage.