The cheap, easy, and fast production of synthetic drugs have radically transformed illicit drug markets around the world, with "lethal results," the United Nations warned on Sunday.

While more people are battling drug addiction, criminals continue to exploit conflicts and global crises to expand drug production, the United Nations Office on Drugs and Crime (UNODC) said in its annual report.

"Fentanyl has drastically altered the opioid market in North America," the UNODC said in a statement accompanying the report.

In 2021 alone, the majority of about 90,000 opioid-related overdose deaths in North America involved synthetic opioid.

Moreover, there are signs that the conflict in Ukraine "could trigger an expansion of the manufacture and trafficking of synthetic drugs, given the existing know-how and the large markets developing in the region," it said.

The expected "drastic drop" in opiate cultivation in Afghanistan following a national ban on growing opium poppy could likely "drive a shift towards synthetic drug manufacture."

The region is already one of the main producers of methamphetamines – the world's dominant synthetic drug.

"We need to step up responses against drug trafficking rings that are exploiting conflicts and global crises to expand illicit drug cultivation and production, especially of synthetic drugs," said UNODC Executive Director Ghada Waly.

The Amazon basin has been particularly hard hit by a flourishing cocaine industry, with trafficking "accelerating crime and environmental devastation," including through illegal logging, mining, land-grabbing and wildlife trafficking.

Globally, more than 296 million people used drugs in 2021, amounting to an increase of 23 percent over the previous decade, the report found.

Meanwhile, the number of people who suffer from drug use disorders has skyrocketed to 39.5 million, a 45 percent increase over 10 years.

Only one in five people received treatment in 2021, the UN said.