No clash has occurred on Mekong River during a four-country joint patrol operation, a Thai marine police officer said on Monday, denying an earlier report by the Thai media.

The report, posted on the website of the Bangkok Post, cited security sources as saying that three Myanmar soldiers were killed in a clash on Sunday with a group of armed people on the Mekong River around 20 km north of the Golden Triangle.

However, Col. Anake Songprasert of Marine Police Division based in Samut Prakan province, told reporters that no clash happened on the river on Sunday. He participated in the 240-km joint patrol to escort ships from Guanlei in China's southwest Yunnan province to Chiang Sean in northern Thailand.

Meanwhile, China's Ministry of Public Security said Monday that all Myanmar crew and patrol boats had returned safely to Myanmar's Wan Pung port Sunday night.

A Myanmar Ministry of Information official also told Xinhua that the Myanmar authorities did not receive any information about the clash.

China, Laos, Thailand and Myanmar began their coordinated patrols on the violence-troubled Mekong River Saturday following the killing of 13 Chinese sailors on the Thai section of the river in October.

Nine Thai army men have been charged with murder and tampering with evidence in connection with the killing of the Chinese sailors.