NAIROBI - Somali pirates have hijacked a Norwegian owned chemical tanker in the pirate-infested waters off the coast of the Horn of Africa nation, a regional maritime official confirmed on Saturday.

Andrew Mwangura, East Africa Coordinator of the Seafarers Assistance program said the South Korean operated, Malta-flagged Samho Jewelry was hijacked on Saturday with 21 crew members onboard.

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"The ship was 10,000-dwt chemical tanker, Samho Jewelry with 21 crew members from South Korea, Myanmar and Indonesia," Mwangura told Xinhua by telephone from Mombasa

He said the vessel was on her way from the United Arab Emirates to Sri Lanka.

The pirates have intensified their action in the Indian Ocean and Gulf of Aden and most of hijackings end without casualties when a ransom has been paid, but often after several months of negotiations.

The Gulf of Aden, a body of water between Somalia and Yemen, is the main sea route between Europe and Asia. Tankers carrying Middle East oil through the Suez Canal must pass first through the Gulf of Aden.

About four percent of the world's daily oil supply is shipped through the gulf.

The attacks are being carried out by increasingly well- coordinated Somali gangs armed with automatic weapons and rocket- propelled grenades, maritime officials said.

The Horn of Africa nation has been without a functioning government since 1991, and remains one of the world's most violent and lawless countries.