Man punched to ground in Cross

A man has been punched to the ground, cutting his head in a brawl at Sydney's King Cross.

The 18-year-old was assaulted at about 1am (AEDT) on Thursday after two groups of men had an argument at a bar on Bayswater Road.

Both groups left the bar but then brawled near the intersection of Darlinghurst Road, both dispersing after the 18-year-old was punched and fell to the ground.

He was taken to St Vincent's Hospital and treated for a cut to the head.

A police spokeswoman said on Thursday morning he was still in hospital because he was too intoxicated to be properly assessed by doctors.

Police say four men they want to speak to were seen getting into two taxis.

A crime scene has been established and police are urging anyone with information to contact them.