Potent new synthetic opioids that mimic the effects of heroin and morphine are a growing health threat in the European Union, the bloc's drug agency has warned.
The Lisbon-based European Monitoring Centre for Drugs and Drug Addiction also expressed concern in its annual report about a rise in drug overdose deaths in 2016 for the third consecutive year.
Young people are exposed to increasing numbers of new and dangerous drugs, according to the agency. They include powerful synthetic opioids that are now also available as liquids and nasal sprays.
"With only small volumes needed to produce many thousands of street doses, new synthetic opioids are easy to conceal and transport, posing a challenge for drug control agencies and a potentially attractive commodity for organised crime," the European Drug Report said.
On average, the agency identified more than one new psychoactive substance coming on to the EU black market each week in 2016.
At the end of last year, it was monitoring more than 620 new psychoactive drugs that had appeared in recent years.
Europe's most commonly used illicit drugs are cocaine, MDMA - also known as ecstasy - and amphetamines.
The annual report also included the results of two surveys of 15 and 16-year-olds in the EU and United States, which indicated a decline in drinking and smoking tobacco among the school students, while cannabis consumption remains largely unchanged.