Two arrested over Sydney teen stabbing

A man and a woman have been arrested over the unprovoked stabbing of a teenage boy outside a shopping centre in Sydney's inner west.

The 29-year-old man and a 23-year-old woman were arrested on Saturday less than 500 metres from the Balmain shopping centre where a 16-year-old local boy was wounded in an unprovoked stabbing on Thursday evening, police say.

Acting Superintendent Anthony Bell said the injured boy and his brother, 14, were confronted outside a Woolworths in Balmain by a man.

The man allegedly asked for a cigarette lighter before gashing the teen's abdomen.

Police described the attack as "swift and unprovoked" while a witness told Channel Nine "there was just blood all over the floor".

The 16-year-old underwent surgery and is now in a stable condition, police say.