China has added 32 designer drugs to its list of controlled substances, the Ministry of Public Security said on Wednesday.

The latest batch of new psychoactive substances, or NPS, added to the list include 4-CEC and 4-EMC. They will be banned in China starting next month.

NPS are stronger than traditional narcotics, such as heroin or methamphetamine, and have caused serious problems for society, Deng Ming, deputy director of the ministry's Narcotics Control Bureau, said at a news conference.

Police used to have difficulties fighting the drugs "because we had no legal basis for crackdowns", he said, but any substance on the controlled list can be seized.

So far, 170 kinds of NPS have been listed as controlled substances, according to the ministry. Since last year, police have uncovered seven cases involving such substances and detained 53 suspects.