FACTBOX - Ships held by Somali pirates

(Reuters) - Somali pirates seized a British-owned ship operated by an Italian company on Monday, after taking three other ships over the weekend, a maritime official said.

A Taiwanese fishing vessel could also have been taken near the Seychelles on Monday, said Andrew Mwangura of the Mombasa-based East African Seafarers' Assistance Programme.

There have been at least 15 pirate attacks on vessels off the coast of Somalia which were reported by the International Maritime Bureau for March, after only two in January and February. Earlier hijackings focussed on the Gulf of Aden.

Below are some of the ships believed to be still held by pirates as well as some details on the increase in piracy:

STOLT STRENGTH: Seized November 10. The chemical tanker had 23 Filipino crew aboard. It was carrying nearly 24,000 tonnes of oil products.

CHEMSTAR VENUS: Seized November 15. The tanker was travelling from Dumai, Indonesia, to Ukraine. It had 18 Filipino and five South Korean crew.

NAMES UKNOWN: Seized on December 10. Pirates hijacked two Yemeni fishing vessels with a total of 22 crew in coastal waters in the Gulf of Aden. Five crew reportedly escaped.

NAMES UNKNOWN: Seized on December 16. A yacht with two on board, an Indonesian tugboat used by French oil company Total. Pirates also hijacked the Chinese fishing vessel Zhenhua-4 with 30 Chinese crew aboard but it was freed the next day.

LONGCHAMP: Seized on January 29, 2009. The liquefied petroleum gas tanker, built in 1990, had 13 crew on board, 12 Filipinos and one Indonesian. The tanker has a capacity of 3,415 tonnes.