(QHA) -

A lethal health crisis is brewing in Crimea and war-torn eastern Ukraine, where injecting drug users have lost access to therapy to wean them off heroin, the UN's AIDS envoy said Wednesday.

Out of 805 people in Crimea who before the unification with Russia were receiving opioid substitution therapy (OST) -- a tried and tested UN-backed treatment -- "between 80 and 100" have now died, Michel Kazatchkine told journalists, AP reports.

"The causes of death, from what we have been hearing, are mainly from suicide and overdose," he said, outlining a report that he said will be handed to UN Secretary Ban Ki-moon.

A "humanitarian crisis" is also developing for different reasons in eastern Ukraine, where the Ukrainian government has stopped providing OST drugs to rebel-held territory, said Kazatchkine.

Lack of the therapy not only endangers addicts, who turn to dangerous street drugs to feed their craving, but also fuels one of the world's fast-growing HIV epidemics, said Kazatchkine, Ban's special envoy for AIDS in Eastern Europe and Central Asia.