“Three Swedish navy warships and a German navy patrol airplane will shortly reinforce the existing European force made up of eight ships and two planes,” Captain Juan Garat Carame said on Wednesday in a Spanish defence ministry statement.

The EU anti-piracy mission Atalante, its first-ever naval operation, began operations off the coast of Somalia in December 2008 in an effort to stop attacks in the Gulf of Aden, one of the world’s busiest trade routes.

Spain took over the command of the mission from Britain earlier this year.

Last month the EU’s foreign policy chief, Javier Solana, said the bloc may extend the mission beyond its December 2009 completion date.

Sweden plans to send two corvettes, one support ship and a security force of about 160 personnel to help defend shipping lanes off the Somali coast.

In addition to the EU force, the United States, Russia, India, Turkey, China and others have deployed warships to protect international shipping. The pirates appear undaunted, however, and have even stepped up attacks.

Ransom-hunting Somali pirates attacked more than 130 merchant ships in the region last year, an increase of more than 200 percent on 2007, according to the International Maritime Bureau.

They currently hold at least 18 ships and close to 300 seamen to ransom.