The Mekong snakes from China into Southeast Asia, where it forms part of Thailand's border with Myanmar and Laos

At least 13 Chinese sailors have been killed in an apparent attack by drug smugglers on the Mekong River between Thailand and Myanmar, prompting the Chinese foreign ministry to call for better protection for its citizens in the area.

Thai officials told China's Xinhua news agency on Monday that 13 sailors were confirmed dead after traffickers hijacked two cargo ship last week in the "Golden Triangle" of the Mekong, a region of Southeast Asia notorious for narcotic production.

Thai police have launched an investigation into the incidents and are hunting the attackers, China's consulate general in northern Thailand told Xinhua.

In a statement, China's foreign ministry said it had "asked the countries concerned to take effective measures to strengthen protection of Chinese vessels and crew on the Mekong River".

China's growing presence in Asia, Africa and other parts of the world has prompted attacks, kidnappings and hijackings, and the issue has become a sensitive one for Chinese officials, who do not want to appear weak in protecting nationals.

Crew on another boat that witnessed Wednesday's attack said eight or so armed men had stormed the two ships.

Thai river police recovered the two boats after a gunfight with the men onboard and found five sacks holding a total of about 900,000 pills of methamphetamine, an illegal drug better known as "speed", China Daily reported citing Thai media reports.

The Golden Triangle region - where the borders of Myanmar, Laos and Thailand meet - is notorious for the production and trafficking of heroin and other illicit drugs.

In April, three Chinese boats and 34 crew members were taken hostage by pirates along the Mekong in Myanmar but were safely rescued within days.

The Mekong snakes from China into Southeast Asia, where it forms part of Thailand's border with Myanmar and Laos, and in 2001 the four countries signed an agreement to regularise shipping on the river. The 4,900km river also flows through Cambodia and Vietnam.