A teenager was stabbed during an attack by gang of up to 20 men in south-west Sydney, police say.

Between 10 and 20 men attacked the 18-year-old after he refused to hand over some of his belongings as he was walking through Lakemba about 9pm yesterday, police said.

He was stabbed in the back with a knife, but made it to a nearby fire station.

He was taken to St George Hospital, police said.

His injuries are not considered life-threatening.

Anyone with information is asked to phone Crime Stoppers on 1800 333 000.

AAP