The prime suspect in the murders of 13 Chinese sailors on the Mekong River last year denied plotting the attack on Thursday.
Naw Kham and five other suspects went on trial at the Intermediate People's Court of Kunming, capital of Yunnan province in Southwest China, facing charges of intentional homicide, drug trafficking, kidnapping and hijacking.
The alleged head of a Myanmar drug gang, Naw Kham claimed he neither planned nor commanded the attack in October 2011.
The trial of the six suspects, all foreigners or stateless, is expected to last three days.
In a media interview before the trial Naw Kham confessed to the murders but he recanted this in court, saying he was not aware of the attack as he had had not been informed by other alleged members of the gang.
"I did not know about it at that time," he told the court. "They did not tell me. I was only informed afterward."
Naw Kham did say that he was the gang's leader, saying every member called him "the boss".
Naw Kham was dubbed "The Godfather" for allegedly running one of the most notorious armed drug rings on that section of the Mekong River, near the China-Myanmar-Laos border.
According to the bill of indictment presented by prosecutors, a substantial amount of evidence, including DNA results, autopsy reports, witness statements and testimony, will be produced before the court.
The other suspects confessed in court, and expressed their regret for the crimes.
Relatives of those slain, foreign embassy personnel, Chinese legislators, political advisors, experts and members of the media, were present in court. Simultaneous translations were provided.
The alleged gang was busted earlier this year in a joint operation by police from China, Laos, Myanmar and Thailand.
A previous police investigation found that Naw Kham, core members of the gang and a small number of Thai soldiers attacked, hijacked and murdered 13 Chinese sailors on two cargo ships, the Hua Ping and Yu Xing 8, on Oct 5, 2011, near a Thai port on the Mekong River.
According to the prosecutor, the suspects tied up the 13 Chinese sailors and put more than 80,000 grams of methamphetamine drugs on board to frame them.
The court was told that one body was found in the Yu Xing 8 wheelhouse on Oct 5, and the other 12 bodies were taken from the river. They had been blindfolded and their hands had been tied.
Naw Kham was flown to China on a chartered plane in May.
"It is uncommon for foreigners who commit crimes against Chinese nationals outside China to be brought to justice before a Chinese court," Dong Lin, vice-president of the court told reporters before the trial.
Li Ruokun, deputy procurator of the Yunnan Provincial People's Procuratorate, said the trial showed China's resolve to punish cross-border crime and to protect the legitimate rights of its citizens.
Li said the suspects' rights were fully respected.
Lin Li, Naw Kham's lawyer, said her rights to meet the defendant and access his files were guaranteed.
Yang Xueguang, 63, father of one of the victims, said: "I have been waiting for this day for a long time. My son was murdered by them and I want them to pay with their lives.
"My wife and I are too old to work and our 6-year-old grandson lives with us. I really do not know what to do."
Security on the Mekong has improved since the incident, according to a crew member of a boat that plies the waters.
"Security has greatly improved after wiping out Naw Kham's gang. My boat never encountered any attacks since the command center, involving four countries, was set up in Xishuangbanna last year," Luo Jianzhi, a sailor with more than 10 years experience on the river, said.
"The 24-hour joint patrols mean that any cargo ship in distress will get immediate assistance," he said.
Hong Daode, law professor at China University of Political Science and Law, said Naw Kham, and other suspects could face the death penalty if convicted.
"According to the national criminal procedure law the maximum sentence for the crimes is death," he said.
Hong said it's the first time in Chinese judicial history that police officers from Myanmar and Laos will testify. This signals "a breakthrough in judicial operation among China, Myanmar and Laos".
The Mekong, known in China as the Lancang River, is one of the most important waterways in Southeast Asia, linking China, Laos, Myanmar and Thailand.