THE HAGUE, March 24 (Xinhua) -- The third Nuclear Security Summit (NSS) kicked off here on Monday, aimed at preventing nuclear terrorism around the globe.

Addressing the opening session on Monday afternoon, Dutch Prime Minister Mark Rutte said world leaders will discuss how to prevent nuclear terrorism during the summit.

"To be more precise, how can we make sure that nuclear materials won't end up in the hands of terrorists and that nuclear material is used more efficiently and stored more securely," he said.

United Nations Secretary-General Ban Ki-moon said that the primary responsibility lies with national governments to prevent non-state actors and terrorists from acquiring the most devastating weapons.

"But international cooperation and assistance are indispensable," the UN chief said, calling on countries to do more to prevent and detect unauthorized acquisition of material outside of regulatory control.

The opening session was followed by a plenary meeting.

The two-day event seeks to reduce the amount of dangerous nuclear material in the world, improve security of all nuclear material and radioactive sources, and step up international cooperation.

Chinese President Xi Jinping and leaders from more than 50 countries and international organizations have gathered here for the summit.

The NSS has become an important platform to address nuclear security issues since its first meeting in Washington in 2010. The second meeting was held in Seoul in 2012.