HANOI (AFP) - Vietnam's marine police on Saturday said they were questioning eight foreigners suspected of being the escaped pirates who commandeered a Malaysian-flagged oil tanker in the South China Sea for a week.

The unarmed men docked on Tho Chu island, off southwest Vietnam, on a lifeboat on Friday morning after "saying they encountered an accident at sea", Major General Ngo Ngoc Thu, deputy commander of the Vietnam Marine Police, told AFP.

Malaysian authorities have been searching for eight men since Friday when they escaped the MT Orkim Harmony in a lifeboat.

It was the latest vessel to be targeted by increasingly bold pirates behind an upsurge of sea hijackings in South-east Asia in the past two years, typically targeting smaller tankers carrying valuable petrol, diesel or gas oil.

On Saturday, Thu said Vietnam was tipped off by Malaysian authorities about the eight "suspects", whose nationalities have not yet been determined, and that they had been sent to the larger Vietnamese island of Phu Quoc for questioning.

"If they are the hijackers Malaysia is looking for, we will follow the laws, relations between the two countries and international practice to handle the situation," he told AFP.

MT Orkim Harmony, carrying around 6,000 tonnes of petrol worth an estimated US$5.6 million (S$7.5 million), went missing on June 11 en-route from Malaysia's western coast to the port of Kuantan on the east coast.

The vessel's 22 crew members were unscathed except for a slightly injured Indonesian seamen who was being treated for a gunshot wound to the thigh, the Malaysian navy said Friday.

The pirates had managed to slip away by ordering naval vessels to stay at least five nautical miles from the ship or the crew would be harmed.

The London-based International Maritime Bureau has repeatedly warned that South-east Asian waters are now the world's most piracy-prone, calling for decisive action by regional authorities to prevent the situation spiralling out of control.