BANGKOK (AFP) - At least 13 Vietnamese passengers were killed on Monday when their van collided with a truck as they travelled to north-eastern Thailand, police said.

Four other people were seriously injured in the pre-dawn accident in Chaiyaphum province, a district police chief told AFP.

The van was carrying 16 Vietnamese travelling from Bangkok to Nong Bua Lamphu province for a Christian seminar, said the police chief Panas Boonyangyao.

He said the truck driver told police that the van inexplicably careered into his vehicle.

Thailand's roads are among the world's deadliest and accidents are common.

A recent report by the World Health Organisation said Thailand saw 38.1 road deaths per 100,000 people in 2010 - behind only the Dominican Republic in the Caribbean and the South Pacific island of Niue.