Image caption The six defendants were extradited to China to face trial in May

A Chinese court has sentenced a Burmese drug smuggler to death over the murder of 13 Chinese sailors on the Mekong river, state media report.

Naw Kham was extradited to China in May to stand trial over the deaths.

Three other members of his gang also received the death penalty and two more were jailed by the court in Kunming.

The 13 crew members were found dead in two Chinese cargo ships on the Thai side of the Mekong in October 2011.

Officials say the Hua Ping and Yu Xing 8 ships were attacked on 5 October as they sailed on the river in the Golden Triangle, where the borders of Laos, Burma and Thailand meet.

There is a great deal about this case that is not clear or simple Head: Mekong murder mystery

All six men were charged with "intentional homicide, drug trafficking, kidnapping and ship hijacking", Xinhua news agency said.

The nationality of five of the men remains unclear. All six will appeal, the Xinhua report said.

Naw Kham has been described as a warlord from Shan state believed to be behind a drug-smuggling network in the Golden Triangle.

Nine Thai soldiers have also been named as suspects in the case - about which much remains unclear.

The killings caused outrage in China and prompted Beijing to send gunboat patrols to the Mekong.