An Islamic State group suicide bomber on Thursday detonated an explosives-packed vest in a mosque inside a Saudi special forces headquarters killing 15 people.
In the latest in a string of IS attacks in the kingdom, the interior ministry said the bomber struck during noon prayers in the city of Abha, in the southern province of Asir near the border with war-strewn Yemen.
Twelve of those killed were members of a Special Weapons and Tactics (SWAT) unit, while the other three were workers at the compound, officials said. Seven other people were wounded.
"The terrorist attack struck worshippers during prayer," the spokesman said, giving an initial toll of 10 policemen and three workers killed and nine people wounded.
El-Ikhbariya state television later said that two policemen wounded in the "heinous" attack had died, bringing the death toll to 15.
IS affiliate "Al-Hijaz Province" said in an online statement that it was behind the attack, the latest — and deadliest — against security forces in Sunni-ruled Saudi Arabia in recent weeks.
The statement identified the bomber as Abu Sinan al-Najdi and said the jihadist infiltrated the special forces headquarters in Abha and activated his explosives vest, killing and wounding dozens.
Al-Hijaz Province vowed to carry out fresh strikes against "tyrants in the Arabian peninsula… in the coming days".
Another IS-affiliated group, "Najd Province", had claimed attacks on Shiite mosques in May that killed 25 people.
An interior ministry spokesman said that "body parts found at the scene" indicated the use of an explosive vest.
The governor of Asir province, Prince Faisal bin Khaled bin Abdul Aziz, visited the mosque and the wounded in hospital.
"The attack is aimed at destabilising the country and sowing fear among citizens," he said, quoted by the official Saudi Press agency.
IS has committed atrocities in Syria and Iraq, where it controls swathes of territories, and expanded across the region, claiming responsibility for a wave of deadly attacks from Libya to Kuwait.
The group has said it was behind a July 16 car bomb that exploded at a security checkpoint near a prison in the Saudi capital Riyadh, killing the driver and wounding two policemen.
Officials identified the driver as a 19-year-old Saudi man and said he had killed his uncle, a colonel, before blowing himself up on a road near Al-Hair prison, a high security facility.
IS said the attack was a message to jihadists held at Al-Hair that they had not been forgotten.
Two days later, Saudi Arabia said it had broken up an IS-linked network and arrested more than 430 suspects involved in attacks and plots.
The interior minister said the suspects had plotted attacks on an unidentified diplomatic mission and mosques, including one used by security forces in Riyadh.
In the southwestern city of Taif on July 3, a policeman was gunned down during a raid in which three people were arrested and IS flags found.
The IS-affiliate Najd Province, apart from the attacks in Eastern Province, also claimed a suicide bombing that killed 26 people at a Shiite mosque in Kuwait in June.
IS considers Shiites to be heretics.
Saudi Arabia and its Sunni Gulf neighbours last year joined a US-led military coalition bombing IS in Syria, raising concerns about possible retaliation in the kingdom.
The kingdom also leads a coalition that has launched air strikes since March against Shiite rebels who have overrun much of neighbouring Yemen and forced the government into exile.
Al-Qaeda waged a campaign of shootings and bombings against foreigners and Saudi security personnel between 2003 and 2007.