Pakistani police say a head-on collision between a passenger bus and a truck on a highway in the country's south has killed at least 50 people.

Police official Ghulam Jhokhio says the accident happened on Tuesday morning near Khairpur district in Sindh province. He says the cause of the accident was most likely heavy fog.

Jhokhio says the bus was carrying about 70 people. It had left the Swat Valley and was en route to the southern port city of Karachi when it collided head-on with the truck.

Local hospital official Jafar Soomro says 14 women and eight children are among the fatalities.

Deadly accidents are common in Pakistan due to bad road infrastructure and disregard of traffic laws.