Four men die in 45 minutes on NSW roads

Four men, all aged in their 20s, have died in two separate crashes in less than an hour on Sydney's outskirts.

Three men, all passengers in an SUV, died in a head-on collision with a car at Kurmond about 3.30pm on Sunday, police said.

The driver of the four-wheel drive in the Kurmond crash and the car driver and passenger, a couple aged in their 80s, were all taken to the Westmead Hospital with serious injuries.

Police crash investigators are at the scene on the Bells Line of Road and have appealed for witnesses to come forward.

Just 45 minutes earlier, a man in his 20s, died after his motorcycle and a car collided at Picton.