The accident on Wednesday took place on Hijra road, 170 km from Madina, when a privately chartered bus carrying 39 passengers collided with a loader, a spokesman for Madina police said, according to the official Saudi Press Agency.
Those on the bus were expats in the Kingdom and of Asian and Arab nationalities, reported Arab News.
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 Makkah.
In January 2017, six Britons, including a two-month-old baby, were killed in a minibus on their way to Madina after making a pilgrimage to Makkah.
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.