The Islamic State (IS) is targeting the Sunni-Shiite sectarian divide in Saudi Arabia to create discord and undermine the royal family's rule. The kingdom is vulnerable to sectarian strife given the family's intimate connections to the Wahhabi Sunni clerical establishment, years of suppression of Shiite Saudis and the war in Yemen.

The first IS terrorist attack on Saudi Shiites took place in November. This month there have been two suicide attacks on Shiite mosques on successive Fridays. The first killed 21 worshippers inside a mosque, the second bomber was stopped outside the mosque before blowing himself up, killing four.

Caliph Ibrahim, or Abu Bakr al-Baghdadi, has publicly called for the downfall of the House of Saud. IS claims it has already established an underground infrastructure in what it calls the "vilayet of the Nejd." Saudi authorities have arrested dozens of Saudis accused of belonging to IS cells.

By attacking Shiite mosques and other soft targets, IS hopes to fan sectarian tensions and exploit Sunni hatred for Shiites to build a cadre inside the kingdom. The Saudi family has condemned the attacks and promised to destroy IS cells inside the country. King Salman bin Abdul-Aziz Al Saud has promised swift punishment.