Four synthetic drugs more powerful than heroin will be banned in China from July 1.

The new psychoactive substances, or NPS, known as U-47700, MT-45, PMMA and 4,4’-DMAR will be added to the nation’s list of controlled substances, the Ministry of Public Security said on Monday.

"NPS have a similar or stronger effect than traditional drugs, including heroin or crystal meth,"Deng Ming, deputy director of the ministry’s Narcotics Control Bureau, said at a news conference.

The narcotics were developed in labs by making subtle changes to the chemical structures of traditional drugs to bypass the law.

NPS can cause significant damage to the central nervous system, with U-47700 being 7.5 times stronger than morphine, according to Yu Haibin, a senior official with the Narcotics Control Bureau.

So far, 138 kinds of NPS, including 23 kinds of fentanyl, have been listed as controlled substances in China.

Since 2009, NPS abuse has become widespread globally, with nine categories of NPS involving 789 subcategories discovered around the world, the ministry said.

Since October 2015, Chinese police have arrested 10 people on suspicion of producing or trafficking NPS, and destroyed eight drug dens used to illegally manufacture such substances.

The ministry said police have confiscated 1,753 kilograms of banned NPS.