Two men on the run after allegedly stabbing another man in Darlinghurst

Two men are on the run after allegedly stabbing another man in the chest in Sydney's inner city.

Emergency services were called to Liverpool Street, Darlinghurst, about 1pm on Wednesday and treated an 18-year-old man for multiple stab wounds to his back.

The victim has been taken to St Vincent's Hospital in a critical condition.

A school in the area was locked down as a precautionary measure but has since been reopened.

Police are searching for two men, aged between 18 and 25.

Investigations continue.

More to come