U.N. Secretary-General Ban Ki-moon on Tuesday paid tribute to those affected by the Chernobyl nuclear accident on the 25th anniversary of the explosion there, and called for steps to further examine and strengthen nuclear safety. "At a time when both the adverse effects of climate change and the demand for nuclear energy are expected to grow, serious global debate on how to ensure the peaceful uses of nuclear energy and maximum safety has assumed great significance," Ban said in a statement. The worst nuclear accident in history occurred at the Chernobyl nuclear power plant on April 26, 1986. Plumes of radioactive smoke spread for thousands of square miles across Ukraine, the former Soviet Union, Europe and Scandinavia. Ban marked the anniversary by ringing the U.N. peace bell in the gardens of the global organization's headquarters on the east side of Manhattan, New York City. "Once again, I call on the international community to support the full recovery of all communities affected by the Chernobyl disaster," Ban said. "Science tells us that normal life is fully possible for most people in these areas, but investment and jobs are crucial." Following the ceremony, the U.N. General Assembly held a special commemorative session on Chernobyl where Ban laid out a five-point plan for the future of nuclear safety. Ban told the 192-nation assembly that his new plan includes reviews of national and international safety standards and the connection between safe nuclear power and natural disasters, as well as strengthening the International Atomic Energy Agency (IAEA). "We must treat nuclear safety as seriously as we treat nuclear weapons," he said. "It is time to face the facts," Ban said. "Issues of nuclear power and safety are not purely matters of national policy; they are a matter of global public interest." The U.N. chief said he will convene a meeting of world leaders in September to address nuclear safety. "It is time to undertake serious global debate on this issue at the level of global leaders."