The head of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization has highlighted the need to halt nuclear testing for good to prevent nuclear weapons from falling into wrong hands. Tibor Toth, Executive Secretary of the Vienna-based nuclear monitoring group, said in a statement on the observance of the first International Day against Nuclear Tests, on Sunday. He said while too many nuclear weapons remain in so many hands, we cannot ignore the risk of falling into the hands of terrorists. Closing the door on their development, once and for all, will be a critical step towards their elimination.On Aug. 29, 1949, the Soviet Union detonated its first nuclear device at the Semipalatinsk test site in Kazakhstan, four years after the explosion of the first nuclear bomb by the United States. It marked the start of the nuclear arms race between the two powers. On Aug. 29, 1991, the Semipalatinsk test site was shut down on the order of Kazakh President Nursultan Nazarbayev. Last year, the UN General Assembly unanimously agreed to declare Aug. 29 the International Day against Nuclear Tests following a proposal of Kazakhstan.