Police in Bahrain say they've discovered 1.5 tons of explosives in a warehouse and an underground bunker south of the capital, Manama.

Police made the announcement late Wednesday night, saying they found explosive material including C4, RDX and TNT in the Nuwaidrat residential district. Photos offered by police showed drums of what it described as explosive material, as well as hand grenades.

Police said in a statement they made "a number" of arrests, claiming those suspected of being involved had ties to Iran and the Shiite militant group Hezbollah.

The tiny Arab Gulf nation of Bahrain has faced low-level unrest for more than four years, sparked by widespread 2011 protests among the country's Shiite majority demanding greater political rights from the Sunni-led monarchy.

Bahrain hosts the U.S. Navy's 5th Fleet.