The Islamic State in Iraq and the Levant claimed responsibility Friday for a suicide bombing during midday prayer at a Shiite mosque in eastern Saudi Arabia. The Saudi Health Ministry said at least 21 people had been killed and more than 120 others injured.

It appeared to be the first official claim of an attack inside the kingdom by ISIL, which has seized control of much of Syria and Iraq. The group attributed the attack to a new unit, the Najd province, named for the central region of Saudi Arabia around Riyadh. But it was unclear whether the attack was planned by ISIL leaders, initiated independently by a Saudi sympathizer or merely claimed opportunistically after the fact.

The attack was a sign that Saudi Arabia’s intervention in the sectarian conflict in Yemen may be escalating tensions at home.

Members of the Shiite minority in Saudi Arabia have long complained of insults and discrimination by Saudi Arabia’s Sunni majority and its clerical establishment.

During Saudi Arabia’s two-month air campaign against the Houthi movement in Yemen, which practices a form of Shiite Islam and receives backing from Saudi Arabia’s regional rival, Iran, imams at Sunni mosques and commentators in Saudi news media have frequently rallied the public around the war by denouncing Shiites as dangerous infidels.

ISIL leaders have called with increasing vehemence for supporters to carry out attacks in Saudi Arabia, accusing its rulers of hypocrisy. The kingdom’s rulers deny any similarity between their understanding of Islam and that of ISIL.

New York Times