Two people are dead and a dozen are being treated after a multivehicle crash west of the Blue Mountains.

Emergency services are at the scene of the crash on the Great Western Highway, about 15 kilometres north of Lithgow in NSW.

The crash occurred just before 1pm on Friday and involved five vehicles.

Police confirmed that two people had died and about a dozen others were being treated by NSW Ambulance paramedics for various injuries.

Officers established a crime scene and were awaiting the arrival of specialist police.

The Great Western Highway was closed in both directions and was expected to remain a crime scene for a considerable amount of time.

“Emergency services, including RFS crews are in attendance at a significant incident on the Great Western Highway,” the NSW Rural Fire Service tweeted on Friday afternoon.

“The road is closed in both directions between Barton Avenue, Wallerawang, and Range Roadd in Meadow Flat and will be for some time.”

Drivers were urged to avoid the area.

-AAP