Leaders attending the fourth and last Nuclear Security Summit (NSS) in Washington urged broader and more inclusive efforts to ensure global nuclear security on Friday.

Leaders and envoys from 52 countries and four international organizations attended the summit and they discuss ways to build on the progress achieved in nuclear security.

They agreed more efforts and international cooperation are needed to prevent nuclear terrorism and promote disarmament.

The leaders said in a joint communique at the end of the summit on Friday that this year's meeting will be the last. They stressed the role of the United Nations, the International Atomic Energy Agency (IAEA) and other entities in expanding cooperation in nuclear security.

"The UN can contribute to the development of a regime for nuclear security," South Korean President Park Geun-hye said during a working lunch at NSS on Friday.

Park said the IAEA, Interpol, the Global Initiative to Combat Nuclear Terrorism (GICNT) and the Global Partnership should help strengthen nuclear security.

South Korea plans to "assist IAEA activities with a focus on coming up with measures to cope with the threat of cyber attacks," Park said.

"This summit is not the end of our quest to make the world safe from nuclear terrorism," said Dutch Prime Minister Mark Rutte.

He said the leaders at the Washington summit were passing the baton to international organizations.

U.S. President Barack Obama, the architect of the NSS, said the global effort to secure world's nuclear materials from wrong hands was "by no means finished" upon the close of the last such summit.

He said world leaders had made "significant, meaningful progress" to prevent nuclear materials being reached by the terrorists, but there was still a large amount of nuclear and radioactive material that must be secured.

"More work remains to be done to prevent non-state actors from obtaining nuclear and other radioactive materials, which could be used for malicious purposes," said the leaders in their communique on Friday.

The leaders reaffirmed "the essential responsibility and the central role" of the IAEA in strengthening the global nuclear security architecture and in developing international guidance.

They also reiterated the IAEA's "leading role in facilitating and coordinating nuclear security activities among international organizations and initiatives and supporting the efforts of States to fulfill their nuclear security responsibilities."

In a speech delivered at the NSS opening plenary Friday, Chinese President Xi Jinping urged countries around the world to increase national input and expand international cooperation to further firm up the global nuclear security architecture.