BEIJING (AP) — A Chinese court sentenced four members of a Burma drug gang to death Tuesday for kidnapping and killing 13 Chinese sailors last year on the Mekong River, state media said.

China, Burma, Laos and Thailand began joint Mekong River patrols in December after the sailors were killed along a section of the river flowing through the Golden Triangle region, which is notorious for drug traffickers and extortion gangs.

Gang leader Naw Kham was extradited from Laos by Chinese authorities in May. He and three members of his gang were sentenced to death by the People’s Intermediate Court in Kunming, the capital of Yunnan province, the official Xinhua News Agency reported.

Xinhua said another gang member was given a suspended death sentence and one was sentenced to eight years in prison.

All six defendants were charged with intentional homicide, drug trafficking, kidnapping and ship hijacking. All told the court they would appeal, Xinhua reported.

Sailors shipping Chinese produce and manufactured goods down the Mekong have long complained of armed gangs that loot their boats or demand cash. Little action was taken to protect them until the Oct. 5, 2011, attack near the Thai-Burma border, which sparked Chinese demands for a thorough investigation.