BEIJING, June 26 (Xinhua) -- Chinese police last year extradited from neighboring countries or arrested in border areas 37 Chinese nationals wanted as suspected leaders of drug trafficking rings, according to the Ministry of Public Security.

The ministry listed 85 suspected cross-border drug dealers in last year's drug trafficking crackdown, Tuesday's Legal Daily newspaper reported.

Police intensified cooperation and information exchanges with counterparts in Myanmar, Laos, Thailand, and Philippines to combat cross-border drug crimes, the paper reported.

Deputy Minister of Public Security Zhang Xinfeng said overseas and domestic drug traffickers had long transported drugs from northern Myanmar to China using other people.

"Though they are just a few in number, they do great harm," Zhang said.

In 2006, the ministry dealt with 46,000 drug-related cases, broke 745 drug-smuggling rings, destroyed 186 illegal drug factories, and arrested 56,000 people in connection with drug crimes.

They also seized 5.79 tons of heroin, 5.95 tons of crystal methamphetamine, 1.69 tons of opium, 454,000 ecstasy pills, and 1.78 tons of ketamine.

Zhang said great efforts were made to deal with drug-related cases at public entertainment places, so the spread of new types of drugs, like ice, ecstasy and ketamine, were curbed.

The crackdown had resulted in short supplies for heroin addicts, so other narcotics were filling the gap.