NATO agreed Monday to extend its anti-piracy mission off the coast of Somalia until the end of 2014, stressing that foreign navies are helping to reduce the number of hijackings.

Operation Ocean Shield, which currently has four warships at sea, has patrolled the Horn of Africa, acted to disrupt armed robberies on the high seas and escorted UN ships bringing aid to Mogadishu since 2008.

The international efforts are "making a difference, with the number of successful pirate hijacking down significantly in 2012," NATO Secretary General Anders Fogh Rasmussen wrote on Twitter.

"Our message to the pirates is clear, your ability to threaten shipping is diminishing and NATO resolve is not going away," he said, announcing that NATO's decision-making body, the North Atlantic Council, extended the mission.

The European Union, which has deployed its own counter-piracy operation, will consider this week whether to allow its warships to fire at trucks, supplies, boats and fuel stocked by pirates on the beaches.

NATO, however, has decided to continue limiting its mission to sea operations.