KUALA LUMPUR: Malaysian authorities have extended by six days a detention order against seven Somali pirates captured by Malaysian forces last month in a raid to free a hijacked oil tanker in the Gulf of Aden.

A police spokesman told AFP that investigators need more time to complete their probe into the case, a historic bid by an Asian country to prosecute bandits operating off the coast of lawless Somalia.

"The extended detention is to enable police to complete their investigations," a spokesman from police headquarters in the capital Kuala Lumpur told AFP.

The seven have been held on remand in Malaysia since January 31 when they arrived on board the tanker MT Bunga Laurel, which was seized by pirates along with its crew of 23 on January 20.

The tanker was headed to Singapore with a cargo of lubricating oil worth more than $10 million when high-seas bandits armed with AK-47 assault rifles boarded and took control of the ship.

Malaysian naval commandos from a vessel protecting shipping in the Gulf of Aden, along with a navy attack helicopter, responded to a distress call and captured the pirates after a brief firefight.

A day later, South Korean forces captured another five pirates in a separate raid and transported them back to the port city of Busan where they have been charged with robbery, hijacking and attempted murder.

Malaysia and South Korea could become the first Asian nations to prosecute Somali pirates, as affected countries move towards dealing with the piracy crisis off Somalia -- which has surged in recent years through legal action.

Malaysian Attorney General Abdul Gani Patail has promised that the seven alleged pirates will be treated as in any other criminal case, with an investigation followed by a trial.