A "terrorist" bomb targeting a mosque used by Saudi police killed at least 17 people on Thursday in the southern city of Al Abha, state television El Ikhbariya reported.
The explosion took place during noon prayers at a mosque used by Saudi special forces in Al Abha, the broadcaster said, describing it as a "terrorist" attack. It gave no further details.
The interior ministry said 10 of those killed were security personnel and three were workers in the area, according to state news channel Al Ekhbariya. The ministry also said that remains of the bomber indicated that he was wearing a suicide belt.
An interior ministry spokesman confirmed the attack but gave a slightly lower toll of "more than 13" dead.
The victims were members of a Special Weapons and Tactics (SWAT) unit, the spokesman told AFP.
"It's confirmed there's an explosion and there's more than 13 (killed)... in a mosque," the spokesman said.
The explosion happened at the headquarters of the SWAT team, which is tasked with domestic security, he added.
It was too early to say who may have carried out the attack, he added.
Saudi Arabia has been on alert for attacks by the Daesh terror group, who have been blamed for killing policemen and for slaughtering members of the minority Shiite community.
The bombing took place in Al Abha, capital of Asir region in southwestern Saudi Arabia. The region shares a small border with northern Yemen.
