KIEV, April 26 - The leaders of Ukraine and Belarus on Wednesday have toured the site of the 1986 Chernobyl nuclear accident, marking the 31st anniversary of the disaster.

"Both Belarusians and Ukrainians know that the Chernobyl catastrophe knows no borders," Belarusian President Alexander Lukashenko said, adding the accident has seriously affected Belarus.

On April 26, 1986, the fourth reactor at the Chernobyl plant exploded after a safety test went horribly wrong. Winds spread radiation from Chernobyl's ruptured reactor across Belarus' southeastern regions, prompting major alerts in much of northern Europe, including western Russia.

A 2005 United Nations report estimated that 4,000 people could eventually die from the invisible poison, but in a later report, environmental group Greenpeace claimed that 100,000 had already lost their lives.

Last year, a giant metal dome funded by more than 40 countries capped the remnants of the plant where 200 tons of uranium remain buried.

Still in place is a 30-kilometer exclusion zone, including the ghost town of Pripyat, whose 50,000 residents were among hundreds of thousands hastily evacuated.

Prime Minister Volodymyr Groysman thanked the more than 600,000 "liquidators" dispatched to try to clean up the site, armed with relatively little protective gear by then-Soviet authorities.

Those still alive now suffer from debilitating radiation illnesses, according to the German education and intercultural exchange foundation IBB based in Dortmund, according to Deutsche Welle. It has links to Chernobyl disaster research centers in Kharkov, Ukraine and Minsk, Belarus and has planned a new web archive documenting the fates of the liquidators.

IBB has also promoted a new book authored by one of them, Oleg Veklenko, now an architecture professor in Kharkov. Ukraine's second-largest city is home to 25,000 Chernobyl disaster evacuees and workers, including 12,000 liquidators.

Wolfgang Mössinger, the German general consul for Ukraine's Donetsk region, said Monday that the liquidators were owed great public respect and support.

"In 1986 over seven months the liquidators built the first protective shell under indescribably atrocious conditions," he said. (dw/ez)