UNITED NATIONS - UN Secretary-General Ban Ki-moon is expected to mark the 25th anniversary of the Chernobyl disaster on Tuesday after he visited the site of the former nuclear plant, calling for efforts to "continue to build an enduring legacy of safety for the future," a UN spokesman said here Monday.

Martin Nesirky, the UN spokesman, told a daily news briefing that "The secretary-general will mark the 25th anniversary of the Chernobyl disaster tomorrow with a message, noting that, during his visit to Chernobyl last week, he witnessed the devastation first-hand."

"The secretary-general says it was a moving experience which provided an opportunity to reflect upon the impact of the disaster, the lives lost or changed forever, and to face the harsh reality of illness and environmental damage for generations of the past and future," Nesirky said.

"On this important anniversary, he says, let us resolve to dispel the last cloud of Chernobyl and offer a better future for the people who have lived too long under its shadow," the spokesman said. "'We must continue to build an enduring legacy of safety for the future,' he says."

Last week, the Ukrainian government organized four days of conferences in the capital Kiev to mark the 25th anniversary of the accident, which occurred on April 26, 1986, and sent radioactive fallout over much of Europe.

More than 6,000 cases of thyroid cancer have been detected in people who were children or adolescents when exposed to high levels of fallout in the period immediately after the blast, and at least 28 people have died of acute radiation sickness from close exposure to the shattered reactor, reports said.