A bus carrying pilgrims to Makkah burst into flames after crashing into a bridge, killing 20 people and injuring more than two dozen, Saudi state media reported.
The accident occurred at about 4pm on Monday in Aqabat Shaar of Asir province, Al Ekhbariya TV reported.
The bus had departed Khamis Mushayt and was heading to Abha region.
It comes during the first week of Ramadan when there is surge in the arrival of Umrah pilgrims, and merely months before millions of Muslims are expected to make the annual Hajj pilgrimage.
According to reports, problems with brakes on the bus led to a collision with a barrier at the end of a bridge, which caused it to overturn and catch fire.
"According to preliminary information we have now received, the number of deaths in this accident reached 20, and the total number of injuries was approximately 29," the television channel reported.
It said the victims had "different nationalities", but did not mention them.
Footage showed what appeared to be the burnt shell of the bus.