A Vietnamese court on Monday agreed to hand over to Malaysia eight Indonesians who were arrested last year on suspicion of hijacking a Malaysian-flagged oil tanker, according to reports.

The men washed up on Vietnam's southwestern Tho Chu island on a lifeboat claiming to have encountered an accident at sea in June 2015.

They were taken into custody after officials discovered they were carrying large sums of cash, and were accused of hijacking the MT Orkim Harmony oil tanker.

The group spoke Indonesian, officials said, and both Jakarta and Kuala Lumpur requested to have the men extradited.

"The Hanoi people's court has ruled out a request by the Indonesian embassy to bring back the suspects to its country for a trial," state-run VNExpress news site said.

"The court accepted Malaysia's proposal to extradite the men to Malaysia" based on Vietnam's mutual legal support laws with Malaysia, the report added.

Court officials did not respond for a request to comment Monday, though the report said the suspects have 15 days to appeal the ruling.

MT Orkim Harmony was carrying around 6,000 tonnes of petrol worth an estimated $5.6 million when it was commandeered on June 11 last year en route from Malaysia's western coast to the port of Kuantan on the east coast.

The eight suspected pirates eluded search crews by escaping in a lifeboat under cover of darkness, Malaysian authorities said at that time.

The tanker's 22 crew members were mostly unscathed except for a slightly injured Indonesian sailor who was treated for a gunshot wound to the thigh.

The vessel was the latest ship targeted by increasingly bold pirates behind an upsurge of sea hijackings in Southeast Asia in recent years that have typically aimed at smaller tankers carrying valuable petrol, diesel or gas oil.