The Yemen war has crossed into Saudi Arabia’s Eastern Province. This weekend saw intense gun fights between Saudi Ministry of the Interior police and Shiite militants in the town of Awamiyah near Qatif. Video smuggled out of the Kingdom shows firefights with automatic weapons raging on Sunday night. The MOI announced one police officer was killed and four militants arrested. The Shiites report many more casualties.

The MOI apparently learned that the Shiites were planning demonstrations to protest the Saudi military campaign in Yemen. Operation Decisive Storm is intended to stop the Zaydi Shiite Houthi rebels from taking over the country and deposing its pro-Saudi government. The Royal Saudi Air Force has been bombing targets in Yemen since last month. Riyadh believes the Houthis are proxies for Iran.

Approximately 10-15 percent of Saudis are Shiite, and most live in the oil rich Eastern Province on the Persian Gulf, though a few are located near Yemen in southwest Saudi Arabia. Unrest is frequent and often violent. The Saudi authorities can keep the violence contained but decades of effort have failed to address Shiite anger at what they see as systematic repression of their community.

The unrest could spread across the King Fahd causeway into neighboring Bahrain. Since 2011, Saudi Arabia’s National Guard military forces have been supporting the minority Sunni ruling family in suppressing demonstrations by the island’s Shiite majority.

The unrest in the Eastern Province will not be a surprise to the House of Saud; they probably anticipated the Yemen war would create blowback inside the Kingdom. Saudi Minister of the Interior Prince Muhammad bin Nayef put the MOI on alert at the start of the war. The longer the war continues, the more it is likely to spill over outside Yemen.