(AFP) Pirates who seized four fishing vessels and a pair of barges in Malaysian waters released another four crew members, but are still holding at least eight others on Philippine islands, the coastguard said today.

Coastguard commander Muhamad Muda told AFP the four were released along with their vessel late yesterday after marine police negotiated with the hijackers' representatives.

Muhamad said no ransom had been paid for their release, but that the hijackers were demanding payment for the freedom of their remaining between eight and 10 hostages, all workers on the two barges.

"They are asking for ransom. We are looking for the owners," he said.

A group of pirates wearing army fatiques and carrying M-16 rifles Wednesday seized the fishing vessels with between 16 and 20 crew members and the barges off the Sabah port of Sandakan, on Borneo island.

They towed the boats into waters off the Philippines' Ligiman island.

Muhamad said the hijacking was unrelated to the Abu Sayyaf rebel group holding 29 captives, including three Americans, in the southern Philippines, but was the work of "ordinary sea robbers".

Ransom paid

Twelve crew members from three of the boats were released unharmed yesterday after the boat owners paid the pirates a few hundred dollars.

Muhamad said one barge was being held on Ligiman and the other on nearby Tawi-Tawi island, along with their crews.

The coastguard commander also advised shippers sailing the waters off Kudat, northeast of Sabah's capital Kota Kinabalu and waters off eastern Tawau to be alert and request police protection.

"Avoid night sailing and not to stray near Philippines' waters. Situation in southern Philippines is fraught with uncertainty," he said.

Muhamad said tourists on island resorts off Sabah should feel safe since a security net was in place to keep intruders out.

"The hijacking incident happened far out in the sea," he said.

The United States yesterday raised new concerns for the security of Americans in Malaysia's eastern Sabah state, two months after the Malaysian government bristled at a previous warning over Muslim rebels.

Kidnappers from the group grabbed foreign and Malaysian hostages last year in raids on Sipadan and Pandanan islands in Sabah.

Officials in Manila have also ruled out any link between the hijack and the Abu Sayyaf, who are being pursued by 5,000 troops on the southern Philippine island of Basilan.