Bahraini authorities and the country's main Shiite opposition group say two prominent opposition activists were summoned for questioning in connection with their meeting with a U.S. diplomat who was ordered to leave the Gulf island nation this week.

The Interior Ministry says the head of opposition group Al Wefaq, Ali Salman, and member Khalil al-Marzooq were released after questioning Wednesday. It says they were summoned for violating a government order in relation to their meeting with U.S. Assistant Secretary of State for Democracy, Human Rights and Labor Tom Malinowski.

Bahraini authorities on Monday ordered Malinowski to leave following a meeting with Al Wefaq members.

The move has strained relations between Washington and its longtime Gulf ally Bahrain, which hosts the U.S. Navy's 5th Fleet.