The policemen were taken to hospital and were in a “stable condition”, a spokesman for the ministry said, according to the official Saudi Press Agency.
The blast went off when policemen manning the checkpoint on Al-Hair Road stopped the car for a routine control, said the spokesman.
“The driver blew up the car and killed himself,” he was quoted as saying.
The Saudi authorities were investigating the explosion, which took place on the last day of the holy Muslim fasting month of Ramadan. -AFP