Kuala Lumpur, June 19 (IANS): Eight suspected Indonesian pirates were arrested near the Vietnamese archipelago of Tho Chu Island on Friday, hours after they fled from a hijacked Malaysian oil tanker, media reports said.

"They were caught near Tho Chu Island (by Vietnamese Navy officials). They were on a life raft and claimed they were from a fishing boat that sank... We are checking their story and investigation is under way," the Malaysian Star quoted Malaysia's Navy Chief Tan Sri Abdul Aziz Jaafar as saying.

Earlier on Thursday evening, all eight hijackers fled in rescue boats but the captain of the hijacked tanker informed the authorities only some five hours later as he was threatened by the pirates not to reveal their escape plan, according to the Malaysian Navy chief.

The pirates warned the Malaysian Navy ship following them to keep a five nautical-mile distance, threatening the crew would be hurt if the ship got too close. The pirates said they were heading toward Indonesia's Natuna Islands, according to Xinhua news agency.

The eight pirates reportedly fled around 8.30 p.m. on Thursday.

"We turned our ships around and moved, and while we did that they lowered the boat and fled. We did not suspect that they would do that," the Malaysian Navy chief was quoted as saying.

The vanishing act was discovered five hours later when the oil tanker's captain contacted the authorities.

Abdul Aziz said the pirates did not take petrol.

All 22 crew members, including 16 Malaysians, five Indonesians and a Myanmar citizen were safe.

Malaysia started to pursue the pirates with the assistance of an Australian surveillance plane. Assistance was requested from Vietnam, Thailand and Indonesia.

The tanker was on its way from Malacca to the port city of Kuantan when it was hijacked.