FACTBOX - Ships held by Somali pirates

Somali pirates have released the chemical tanker Stolt Strength, a maritime group said on Tuesday. The Stolt Strength was seized last November with 23 Filipino crew aboard.

The International Maritime Bureau's Piracy Reporting Centre (IMB-PRC) said in its latest report that attacks in the first quarter of 2009 have almost doubled compared to the corresponding period in 2008.

A total of 102 report of global pirate attacks were received by the IMB in the first three months of 2009 - compared to 53 incidents in the first quarter of 2008 - due almost entirely to increased Somali pirate activity off the Gulf of Aden and east coast of Somalia.

These two areas combined accounts for 61 of the 102 attacks this quarter.

YENEGOA OCEAN: Seized Aug. 4, 2008 - The Nigerian tugboat, with around 11 crew aboard was hijacked near Bosasso.

JAIKUR-I: Seized Oct. 2, 2008 - The 21,040 tonne general cargo ship was detained after a dispute with the owners over damaged cargo. Most of the 21 crew were released last week. tonnes of oil products.

MASINDRA 7: Seized on Dec. 16, 2008. The Malaysian-owned tugboat, was seized with a barge off the Yemeni coast. The tug has around 11 Indonesian crew.

SEA PRINCESS II: Seized Jan. 2/3, 2009 - The Yemeni-owned tanker was carrying petroleum products and oil. There were eight Indian seamen among the 15 crew.

SALDANHA: Seized on Feb. 22, 2009. The Maltese-flagged cargo ship, sailing to Slovenia, has 22 crew and was loaded with coal.

SERENITY: The fast catamaran Serenity sailing for Madagascar from the Seychelles with three people on board, was seized in early March.

NIPAYIYA: Seized on March 25. The Greek-owned and Panama-registered was seized by pirates 450 miles from Somalia's south coast.

INDIAN OCEAN EXPLORER: Seized March 2009. The 35-metre boat was built in Hamburg as an oceanographic research vessel. It accommodates around 12 passengers.

HANSA STAVANGER: Seized April 4, 2009. The 20,000-tonne German container vessel was captured about 400 miles off the southern Somali port of Kismayu, between the Seychelles and Kenya. The vessel had a German captain, three Russians, two Ukrainians and 14 Filipinos on board.

MALASPINA CASTLE: Seized April 6, 2009. The 32,500-tonne bulker is UK-owned but operated by Italians.

-- A Taiwanese tuna fishing boat, the WIN FAR 161, is seized on the same day.

SHUGAA-AL-MADHI: Seized April 9, 2009. The fishing boat was seized with 13 crew aboard.

MOMTAZ 1: Seized April 10, 2009. Egyptian fishing vessel was detained with 18 crew.

BUCCANEER: Seized April 11, 2009. The Italian tugboat, owned by Micoperi Marine Contractors, was carrying 10 Italians, 5 Romanians and a Croatian, and was seized towing two barges while travelling westbound through the Gulf of Aden.

IRENE E.M.: Seized April 14, 2009. The St. Vincent and the Grenadines-flagged Greek-owned bulk carrier was hijacked as it travelled through the Gulf of Aden. Its 22 Filipino crew were unharmed.

POMPEI: Seized April 18, 2009. The Belgian dredging vessel and its 10 crew was hijacked about 600 km (370 miles) from the Somali coast en route to the Seychelles. It has two Belgian, four Croatian, one Dutch and three Filipino crew on board.

* PIRACY KEY FACTS:

-- In 2008 there were 293 incidents of piracy against ships worldwide -- 11 percent up on the year before. Attacks off Somalia and in the Gulf of Aden almost trebled.

-- In January 2009, one in every six vessels attacked was successfully hijacked. This increased to one in eight for February 2009 and one in 13 for the month of March.

Nearly 20,000 ships pass through the Gulf of Aden each year, heading to and from the Suez Canal.

Sources: Reuters/Ecoterra International/International Maritime Bureau Piracy Reporting Centre/Lloyds List/Inquirer.net

April 21 (Reuters) -