A suicide attack at a mosque used by the Saudi special forces killed 17 security officers in Abha city on Thursday afternoon, Al Arabiya NewsChannel reported.
According to state-run TV channel El-Ikhbariya, the attack took place during the time of prayer.Saudi Arabia is treating the incident as a terror attack.
At least 25 people were injured in the blast, it was reported.
Reuters reported that the mosque was being used by a state security unit called the Special Emergency Force and all those killed were its members.
A Saudi official told the Associated Press on condition of anonymity that the mosque belongs to the interior ministry emergency services posted in Abha in the southern region of the kingdom.
Middle East Eye reported that the death toll is expected to climb as many have been critically injured.