Nine army men have turned themselves in and confessed to killing 13 Chinese sailors on Mekong River in Golden Triangle earlier this month, Thai police chief said Friday.

The suspects were servicemen of the Third Military Command of the Thai Army, which guards the northern border of Thailand, said Thai police chief Pol Gen Priewpan Damapong.

Priewpan said the army and the government were not behind the killing. He said the police suspect the servicemen acted on the order of some local tycoons and further investigation is underway.

The victims aboard two cargo ships were shot dead by a group of gunmen on Oct. 5 in a section of Mekong River that forms the border of Thailand, Laos and Myanmar. Their bodies were found and salvaged from the river in northern Thailand afterward.