A man has died after his car and a semitrailer collided head-on in southern New South Wales.

Emergency services received a call just before 3am and arrived to find the two vehicles had crashed in the northbound lanes.

The driver, the sole occupant of the car, died at the scene. He has not yet been identified.

The truck driver was not injured and has been taken to Albury Base Hospital for mandatory testing.

Police, NSW Ambulance, RFS and SES were at the scene, about 50 kilometres north-east of Albury, at Woomargama.

Fire and Rescue NSW said it was "quite a nasty accident".

An investigation is now underway into the circumstances leading to the crash, including why the car was on the wrong side of the highway.

The Hume Highway was closed northbound at Woomargama — with traffic being diverted at Table Top via the Olympic Highway to Wagga Wagga, but that has since been lifted.

The traffic diversion added about 40 minutes extra to travel time.

Anyone who has information or who has dash cam footage of the vehicles involved are urged to call Albury Police or Crime Stoppers on 1800 333 000.