PETALING JAYA, MALAYSIA: Malaysian tanker MT Bunga Melati Lima is on its way to the pirates' coastal base of Eyl where six other vessels are being held, said a Somali official.

One of the six vessels is the MISC-owned ship MT Bunga Melati Dua which was hijacked on Aug 19.

Abdulqadir Muse Yusuf, Assistant Fisheries Minister in the northern Somali region of Puntland, said: "The pirates are increasing dramatically in numbers and strength."

The MT Bunga Melati Lima was carrying 30,000 tonnes of petrochemicals from Yanbu in Saudi Arabia to Singapore when it was seized on Friday in the Gulf of Aden.

Thirty-six Malaysians and five Filipino crew were on board when the hijacking took place. The latest incident pushes the number of Malaysians held captive by Somali pirates to 65.

MISC said the tanker had been travelling "within the vicinity" of a security corridor set up last week by a multinational anti-terrorism task force in response to the sharp rise in pirate attacks.

The International Maritime Bureau (IMB) has again called on ships in the Gulf of Aden to keep a strict 24-hour visual and radar watch to avoid being attacked by pirates.

Last week, Somali gunmen seized a record four ships in 48 hours, and are now holding about 130 crew hostage. - Agencies