A Chinese court sentenced a drug baron from Myanmar and three of his alleged gang to death for the killing of 13 Chinese sailors in an attack on the Mekong River.

The gang leader Naw Kham and five gang members were found to have planned -- with the help of Thai soldiers -- the attack on two Chinese cargo ships in October 2011.

The bodies of the 13 sailors were found floating in the river, blindfolded and with their hands tied or handcuffed. All of them had died of gunshot wounds, a report by the Global Times said at the time.

Three other members of Naw's gang were ordered put to death and two more were jailed by the court in Kunming, in Yunnan province in southwestern China.

Naw, 43, and several of gang members also were found guilty of kidnapping Chinese sailors and hijacking cargo ships in exchange for ransom in early April 2011, a report by China's state-run news agency Xinhua said.

The six men were captured in a joint operation by police from China, Laos, Myanmar and Thailand.

The sentences were read out in a large, open courtroom attended by around 300 people, including relatives and friends of the victims, diplomats from Laos and Thailand and the press. The defendants wore headphones to hear translations of proceedings, Xinhua said.

The defendants said they will appeal the sentences.

During their trial in September, Naw pleaded guilty and expressed sorrow for the attack and deaths, offering to pay financial compensation to the families.

Judges in the sentencing hearing ordered the six to pay total compensation of around $960,000, Xinhua reported.

The Mekong is one of the world's longest rivers, running more than 3,000 miles from its source in Tibetan mountains.

It passes through China's Yunnan province, briefly marks the border between Myanmar and Laos, then intermittently between Laos and Thailand. It enters Cambodia and finally Vietnam, forming the Mekong Delta and emptying into the South China Sea.

The Mekong flows through the infamous Golden Triangle area of Thailand, Laos and Myanmar. The triangle is known for opium and heroin smuggling but also is increasingly known for an illicit trade in methamphetamines.

Many ships have been hijacked to quickly move millions of methamphetamine pills along the river as part of the transportation system that includes horse and donkey routes through mountains.

The Xinhua report said Naw is known as the "Godfather" and was the head of the largest armed drug trafficking gang in the Golden Triangle. His gang had pistols, rifles, submachine guns, bazookas and anti-tank grenades.

The attack on the 13 sailors prompted China to close temporarily its part of the river to commercial boats heading south into the Golden Triangle.

Shipping resumed in December after Chinese patrol boats began joint anti-smuggling operations with Laos, Myanmar and Thailand along the Mekong.