A suicide bombing at a mosque in Ashba city in Asir, southwest Saudi Arabia, has claimed the lives of 15. The mosque was part of the local headquarters of a state security unit called the Special Emergency Force.

The suicide bombing is the third to take place in Saudi Arabia this year, following the two suicide bomb attacks on Shia mosques in May. The first one was on a mosque in Qatif, east of KSA, killing 21 worshippers, and the second one was at a mosque in Dammam, killing four, according to The Telegraph.

The blast took place while members of the security forces were in the middle of noon prayers. The timing of the attacks are often intended to maximize casualties and have targeted mosques belonging to the Shiite minority in Saudi Arabia. ISIS claims responsibility over the attack following the two previous attacks in May. The Islamic State consider Shiites heretics, according to BBC News.

Saudi security services have announced in the past months the arrest of hundreds of people across the kingdom supporting ISIS, planning attacks and promoting its ideology. But these efforts have failed, as ISIS has the ability to indoctrinate aspiring militants and even give instructions through the internet, according to the New York Times.

Ten of those who died were members of the security force in the Asir region, while the three others were working on the site.

Asir region includes a small portion of Saudi Arabia's border with Yemen. As a support to the Yemen president, Saudi Arabia launched numerous strike aiming at Houti rebels who took over Yemen's capital, according to CNN.