Bahraini authorities said Monday they have seized a boat smuggling explosives made in Iran and Syria into the Sunni-ruled kingdom, which quashed a Shiite-led uprising in 2011.
The boat, which had two Bahrainis aboard, was stopped over the weekend at two nautical miles (3.7 kilometres) off the archipelago's coast, public security chief Major-General Tareq al-Hasan said.
He said it had been tracked over a distance of 118 nautical miles (218 kilometres) northeast of the kingdom.
"Fifty hand grenades made in Iran," as well as "295 fuses connected to switches labelled as made in Syria," were found in the 29-foot (nine-metre) vessel, he said in a statement carried by state news agency BNA.
Dozens of C4 and TNT explosive devices were also found on the boat, he said, without providing details about the source of the alleged shipment.
Hasan said that security forces also discovered a cache of explosives in a village outside Manama, dismantled a car bomb and arrested 13 wanted people, including a Saudi national, as they attempted to flee Bahrain in a boat.
The Sunni-ruled Gulf monarchies have long accused Shiite Iran of meddling in Bahrain's affairs, while Saudi Arabia and Qatar have strongly supported rebels fighting to topple Syrian President Bashar al-Assad, a close ally of Iran.
Bahrain crushed an Arab Spring-inspired uprising led by members of its Shiite majority in 2011, with Saudi-led Gulf troops aiding in the crackdown.
Since then demonstrations have regularly been held in Shiite villages around the capital, often sparking clashes with security forces.
At least 89 people have been killed in Bahrain since the protests began, according to the International Federation for Human Rights.
Several bomb attacks have also taken place in recent months, including one that targeted a Sunni mosque close to the royal court in July but caused no casualties.
Tensions escalated over the weekend as authorities interrogated top Shiite opposition leader Ali Salman.
The head of the main Shiite bloc Al-Wefaq was released after a day of questioning, but was charged with incitement to religious hatred and spreading false news endangering national security.