Bahrain, a majority Shiite country ruled by a Sunni royal family, the Khalifas, has been roiled by protests since the outbreak of the Arab Spring in 2011. At the height of the demonstrations, with their leadership threatened, the Khalifas called on the Saudi military to restore order.

Since then, Bahrain has emerged as a possible point of contention in the Persian Gulf, with protests and crackdowns. The protest movement has publicly distanced itself from Iran, but leaders in Tehran have often lent vocal support.

Bahrain announced on Monday that it had revoked the citizenship of Ayatollah Qassim, 79. That followed its June 14 suspension of the Wefaq National Islamic Society, the country’s leading Shiite opposition group, which Ayatollah Qassim had led. The decisions to shut down the opposition group and to revoke the citizenship of its spiritual leader, and the arrests of human rights activists, suggest a new crackdown on the island, analysts say.

Saudi Arabia and Iran have been fighting proxy wars throughout the region since 2011, supporting groups in Iraq, Lebanon, Syria and Yemen, as well as in smaller theaters like Bahrain.

In December, Saudi Arabia and Iran clashed over another Shiite Muslim cleric, Nimr al-Nimr, who was executed in Saudi Arabia. Hard-line protesters raided the Saudi Embassy in Tehran after his execution, leading to the severance of diplomatic ties.

Tehran has said Iranians will not participate this year in the hajj, the annual pilgrimage to Saudi Arabia. The hajj was marred last September by a catastrophic stampede that, according to outside estimates, killed more than 2,400 people. Iran said more than 460 were Iranians, among the biggest losses of any country.