Environmental watchdog Greenpeace International says more than 90,000 people have already died or are expected to die from cancer-related diseases as a result of the Chernobyl nuclear accident in 1986.

Data released Tuesday contrast sharply with an earlier U.N. report that estimated the final death toll from Chernobyl would be closer to 4,000 lives.

Serhiy, a school boy, has his thyroid tested for abnormalities March 7, 2006, by a Red Cross unit that travels through rural areas in western Ukraine that were contaminated by the 1986 explosion at the Chernobyl nuclear power plant

Greenpeace says the most recently published figures indicate that the reactor explosion 20 years ago spread enough radioactive material across Belarus, Russia and Ukraine to cause more than a 250,00 cases of cancer. About one-third of those victims - 93,000 people -- are expected to die, or already have died, as a result of their ailments.

The U.N. report on Chernobyl said poverty, depression and stress have posed a far greater threat to the affected communities than radiation exposure. Greenpeace rejected those conclusions and said the United Nations was ignoring the real implications of the disaster.

One of three reactors at a Soviet nuclear power plant in Ukraine exploded on April 26, 1986, spewing a heavy layer of radioactive fallout over much of Europe.