Official discussions focused on how best to secure nuclear material and facilities against terrorists. One of the key pledges was expected to be a reduction in the stockpiles of nuclear material.
"Significant advances must be made in eliminating and minimizing the use of nuclear materials including highly enriched uranium and plutonium, "South Korean President Lee Myung Bak said at a dinner to open the event late Monday.
He also called for "enhancing international cooperation, which is crucial in detecting, tracking and responding to illicit trafficking of nuclear material."
Delegates had agreed that the summit's communique "will pledge to minimize the civilian use of highly-enriched uranium and plutonium," a senior Seoul diplomat was quoted as saying on condition of anonymity by Yonhap News Agency.
The leaders were also to discuss the ability of nuclear facilities to resist natural disasters, after an earthquake and tsunami in March 2011 left a nuclear power station in Japan leaking radioactive material.
The summit was a follow-up to discuss how to implement the objectives agreed at the first nuclear security summit in Washington in 2010.
The nuclear weapons programmes of North Korea and Iran, although not on the official agenda, were widely expected to feature in discussions on the sidelines of the event.//DPA