Across the former Soviet Union, people lit candles, laid flowers and held demonstrations yesterday to mark the 18th anniversary of the Chernobyl nuclear disaster, which spread radiation over much of northern Europe.

　　In all, nearly 7 million people in the former Soviet republics of Belarus, Russia and Ukraine suffered physical or psychological effects of radiation related to the April 26, 1986, catastrophe, when reactor No. 4 exploded and caught fire.

　　An area half the size of Italy was contaminated, forcing hundreds of thousands of people to be resettled and ruining some of Europe's most fertile agricultural land, the United Nations said.

　　Hundreds of Ukrainians filled the small Chernobyl victims' chapel in the Ukrainian capital, Kiev, where they laid flowers and lit candles at a small hill where marble plates are inscribed with the names of hundreds of victims.

　　"Nothing can be compared with a mother's sorrow," said Praskoviya Nezhyvova, an elderly retiree clutching a black-framed photograph of her son, Viktor. She said he died of Chernobyl-related stomach cancer in 1990 at age 44.

　　Soviet authorities had withheld much information on the world's worst nuclear accident. Only last year, Ukraine's security service declassified secret files documenting malfunctions and safety violations at the plant that caused the release of small doses of radiation from time to time long before the explosion.

　　Ukraine shuttered Chernobyl's last working reactor in December 2000.

　　The most frequently noted diseases caused by the accident include thyroid and blood cancer, mental disorders and cancerous growths.

　　(The Associated Press)