Thirty-five foreign tourists were killed and four others injured when a bus collided with another heavy vehicle near the Muslim holy city of Medina, Saudi state media said on Thursday.

The accident on Wednesday involved a collision between “a private chartered bus ... with a heavy vehicle (loader)“ near the western Saudi Arabian city, a spokesman for Medina police said, according to the official Saudi Press Agency.

Those involved were Arab and Asian pilgrims, according to local media, which carried pictures of the bus engulfed in flames and with its windows blown out.

The injured have been transferred to Al-Hamna Hospital, SPA added, and authorities have launched an investigation.

The accident comes after four British pilgrims were killed and 12 others injured in Saudi Arabia when their bus collided with a fuel tanker in April 2018. They were on their way to the holy city of Mecca.

In January 2017, six Britons, including a two-month-old baby, were killed in a minibus on their way to Medina after making a pilgrimage to Mecca.

As part of efforts to diversify its oil-dependent economy, the ultra-conservative kingdom wants to foster a year-round religious tourism sector that includes millions of pilgrims.

Up until last month, the country only issued visas to Muslim pilgrims, foreign workers and recently to spectators at sporting or cultural events, but tourists are now allowed to visit as part of the drive to prepare the biggest Arab economy for a post-oil era.

In September 2015, a stampede killed up to 2,300 worshippers – including hundreds of Iranians – in the worst disaster ever to strike the Hajj annual pilgrimage.