A search is underway for a man who attacked two immigration detention centre contractors transferring him to an airport.

The 28-year-old Tongan man was being driven from Villawood Detention Centre to Sydney Airport when the driver and passenger were attacked with a “sharpened metal object” about 3.40am, police told reporters on Thursday.

A 54-year-old man was stabbed in the neck and a 36-year-old man was assaulted during the attack.

The detainee fled at Clyde with police dogs tracking him as heading towards Harris Park, Superintendent Simon Glasser said.

“We are working closely with Australian Border Force and (the Department of Home Affairs),” he said.

“The victims are contractors who work for Villawood Detention Centre.”

The man is described as unshaven with a large build and about 180cm tall and was last seen wearing a dark jacket and pants with black and white sneakers.

He is known to police and frequents Mount Pritchard and other areas in southwest Sydney.

“This was obviously a violent offence that’s occurred so we do ask members of the public to be wary if they believe they see him and contact us, not to approach him,” Glasser said.

Both contractors were taken to Westmead Hospital but their injuries are not considered to be serious.

-AAP