MANAMA, Bahrain (AP) — Bahrain says authorities have arrested three suspects in connection with a bombing last week outside a mosque near the royal residences in the Gulf kingdom.

The blast pointed to a widening campaign by more militant factions in the opposition. Bahrain has experienced over two years of unrest stemming from the Shiite majority’s demands for a greater political role in the Sunni-ruled island nation, which is home to the U.S. Navy’s 5th Fleet.

Bahrain’s Interior Ministry said Sunday the three suspects were brought before a public prosecutor, but no other details were immediately given. No one was injured in Wednesday’s blast.

The bombing has been denounced by the main Shiite opposition groups. But it suggests a growing presence of hard-line networks that have previously carried out bomb attacks on security forces.