A person has died and three others are in hospital with serious injuries after a two-car crash in a tunnel near Sydney Airport.

The head-on crash happened in the airport tunnel on General Holmes Drive before 5.40am on Thursday, NSW Police said.

Traffic was gridlocked in the area after the fatal crash caused the closure of all southbound lanes in the airport tunnel. Authorities urged drivers to avoid the area.

AIRPORT TUNNEL: General Holmes Dr remains closed southbound due to a fatal crash in the tunnel. Stay away. 1 citybound lane is also closed. There are very long delays in both directions & on all approaches. Catch a @T8SydneyTrains to @SydneyAirport – don't drive. pic.twitter.com/0aJFv5bQ8g

— Live Traffic Sydney (@LiveTrafficSyd) February 5, 2020

Transport NSW said that – due to the serious nature of the crash – it was unable to tell when the road would be re-opened. Later in the morning, a northbound lane was also closed in the tunnel.

NSW police said there were five people in the northbound vehicle, and just the driver in the southbound vehicle. The person who died at the scene was a passenger in the northbound vehicle.

Police have asked anyone with dashcam vision of the crash to contact Crime Stoppers on 1800 333 000.

-with AAP