One driver has died and another is missing after a head-on crash on a NSW highway just after midnight.

Emergency services were called to the Monaro Hway at Colinton, in the Snowy Mountains region, about 12.15am on Sunday following reports two vehicles had collided head-on.

Police arrived to find one driver had died at the scene.

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The person is yet to be formally identified.

The driver of the second vehicle has not been located.

A crime scene has been established and an investigation into the circumstances of the crash is underway.

The Monaro Highway remains closed in both directions between Old Cooma Rd and Yareen Rd as of Sunday afternoon.

Drivers are being urged to avoid the area, delay non-essential travel and use alternative routes.

Anyone with information or dashcam footage is urged to contact Crime Stoppers.