The Islamic State of Iraq and al-Sham conducted two major bombings on Shia mosques in the Arabian Peninsula today [22 May 2015]through its affiliates in Yemen and Saudi Arabia. ISIS claimed responsibility for an IED explosion that injured at least 13 Shia worshippers during Friday prayers in the al Sayyah Mosque in Sana'a, Yemen. ISIS also claimed responsibility for a suicide bombing on the Shia Imam Ali mosque in al-Qadeeh in the Shi'a Eastern Province of Saudi Arabia. This latter attack killed at least 20 individuals and wounding dozens more. In statements circulated by ISIS's supporters on Twitter after the attacks, ISIS reportedly asserted that it would "expel all the unbelievers from the Arabian Peninsula."

ISIS's threat to Saudi Arabia is not new. ISIS declared its intent to attack both Saudi Arabia and Yemen in late 2014. Over the course of this year, ISIS has escalated its activities in both countries in order to increase regional disorder and undermine the Saudi-led Arab coalition. Today's two attacks were possibly coordinated, reflecting an acceleration in an ongoing campaign by ISIS to destabilize Saudi Arabia and gain power in Yemen.