Story highlights Fears pirates have boarded a tanker carrying 5,200 tonnes of oil

Ship went missing on October 2 within an hour of departing Singapore

18 crew were on board the ship which was headed for Vietnam

Vietnamese authorities are searching for an oil tanker feared to have been taken by pirates just 40 minutes after it departed Singapore for Vietnam almost one week ago.

The Sunrise 689 was carrying 18 crew and 5,200 tonnes of oil when it left Singapore's Horizon port on October 2, according to the Vietnamese News Service (VNS).

The ship's owner, the Hai Phong Seafood Shipbuilding Join Stock Company, reported that it lost contact with the ship within an hour of its departure, VNS said.

VNS reported that Vietnam's Foreign Ministry had sent "diplomatic notes" to the embassies of Singapore, Malaysia, Brunei and Indonesia in Hanoi, asking for assistance in finding the missing ship.

Piracy rising in Asia

Southeast Asia has become a prime target for pirates who have staged a number "serious attacks" on tankers in the region, according to the International Maritime Bureau (IMB).

According to a report released in July , there had been at least six known hijackings since April, when small coastal tankers were targeted for their cargo of diesel or gas oil.

"The recent increase in the number of successful hijackings is a cause for concern," IMB director Pottengal Mukundanm said at the time.

Until this year, most attacks had been petty thefts perpetrated on boats anchored at harbor, the IMB said.

The missing ship, Sunrise 689, was last detected in the middle of a busy shipping zone in the Singapore Strait.

According to warnings issued by the IMB , vessels in the Singapore Strait are advised to "remain vigilant and to continue maintaining adequate anti-piracy / robbery watch and measures. Pirates / robbers attack ships while underway or while at anchor especially during the night."

Sunrise 689 had been expected to arrive at Con Son island in southern Vietnam on Sunday, October 5, VNS said.