China and southeast Asian neighbours will start coordinated patrols of the violence-troubled Mekong River by mid-December, a Chinese ministry said, after a meeting that also agreed to let Beijing send advisors to Myanmar and Laos.

The announcement followed an uproar after 13 Chinese sailors were killed on the river last month in an attack that Thai investigators believe may have been carried out by Thai state officials.

The sailors' boats were attacked in the Golden Triangle, where the borders of Myanmar, Thailand and Laos meet in a region notorious for drug smuggling. Nine Thai soldiers later turned themselves in over the killings.

According to the information that we gathered ... it can be believed that Thai officers were involved, Sunai Julapongsathorn, chairman of Thailand's lower house committee on foreign affairs, told reporters in Bangkok on Thursday.

Sunai said he could not confirm whether or not soldiers were involved, but said witnesses had given evidence and police had photographs of a suspect setting up a machine gun used in the killings.

China's Ministry of Public Security said on its website (www.mps.gov.cn) on Wednesday security officials from China, Thailand, Myanmar and Laos agreed at a recent meeting in Beijing to together organise and implement joint operations to attack severe public safety problems menacing security along the river.

The agreement will allow Beijing to send expert support teams to Laos and Myanmar, if those two countries request training help. The report made no mention of Thailand wanting such help.

TROOPS HELD

The police chief in Thailand's Chiang Rai province, Major-General Songtham Allapach, on Thursday said the investigation was being fast-tracked and the nine detained soldiers had denied involvement in the attack.

They are currently in military custody charged with two counts of conspiracy to murder and accused of trying to cover-up the killings by disposing of the bodies.

It would probably take some time for interrogation, he said. The findings and conclusions should be sent to the court sometime next year.

A joint command post for the patrols will be set up in the Chinese river port of Guanlei in Yunnan province, and a maiden patrol will leave from there on an unspecified date before December 15, said the report

In a reflection of territorial sensitivities involved in the joint operations, however, the announcement said they would be based on each country's legal jurisdictional powers and mutual respect for sovereignty and inequality.

The 4,900-km (3,050 mile) Mekong snakes from China into Southeast Asia, where it forms the border between Myanmar and Laos, and then Thailand and Laos. In 2001, the four countries signed an agreement to regularise shipping on the 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.

The Chinese government has bought five ships that will be refitted for the patrols, said an earlier Chinese news report.

(Reporting by Chris Buckley in Beijing and Natnicha Chuwiruch and Aukkapon Niyomyat in Bangkok; Editing by Jonathan Thatcher)