A former senior police narcotics squad officer and two drug traffickers were Monday sentenced to death for murder, drug-trafficking and graft after being convicted at a court in southwest China's Chongqing Municipality.

Luo Li, former deputy chief of the anti-drug brigade of the Chongqing Municipal Public Security Bureau, was convicted of collaborating with and protecting drug traffickers since 2005, said a statement from the No. 1 Intermediate People's Court of Chongqing.

A court investigation found the two drug dealers he protected, Ao Xingman and Zhou Guangquan, trafficked more than 120,000 grams of heroin from 1997 to 2010, the statement said.

In return, Luo accepted 1.2 million yuan in bribes, and paid 400,000 yuan to bribe officials for promotions from 2005 to 2008, it said.

At Luo's instruction, Ao and three accomplices murdered Zhang Hao, a drug trafficker who threatened to give evidence against Luo after his request for protection was rejected. Zhang was shot dead on his way home in July 2002.

Three other members of Ao's ring received jail terms ranging from two to 15 years, the court statement said.

It did not say whether Luo or the drug traffickers would appeal. In China all death penalties are automatically reviewed by the Supreme People's Court, the highest judicial panel.

Luo was one of the police officers ensnared in a gang crime crackdown that gripped the nation with revelations of a thriving underworld in Chongqing led by mob bosses who acted with impunity under the protection of corrupt officials.

More than 3,300 people were detained and hundreds prosecuted in the campaign.

Wen Qiang, a former top Chongqing police and justice official, was executed in July on convictions including rape and taking bribes to protect criminal gangs.