Somali pirates have seized a Singaporean-flagged container ship in the pirate-infested Indian Ocean waters near Seychelles, a regional maritime official confirmed in Nairobi Thursday.

Andrew Mwangura, East Africa Coordinator of the Seafarers Assistance Programme said the vessel owned by boxship Kota Wajar was hijacked early Thursday with 21 crew members.

"The Singaporean flagged ship was hijacked in the Indian Ocean waters, 180 nautical miles northwest of Seychelles. The ship which was coming from Singapore was heading to Mombasa port," Mwangura told Xinhua through telephone from Mombasa.

Mwangura could not however establish the nationalities of the crew members, saying Singaporean vessels now have crew members from different nationalities.

Piracy has become rampant off the coast of Africa, especially in the waters near Somalia, which has been without an effective government since 1991.

Ransoms started out in the tens of thousands of dollars and have since climbed into the millions.

An estimated 25,000 ships annually cruise the Gulf of Aden, off Somalia's northern coast. Over 10 ships and 200 crew members are still held by Somali pirates.

The Gulf of Aden, off the northern coast of Somalia, has the highest risk of piracy in the world. About 25,000 ships use the channel south of Yemen, between the Red Sea and the Arabian Sea.