Full coverage: Xi Visits Czech Republic, Attends Nuclear Security Summit

World leaders reaffirmed their commitment to fight the proliferation of nuclear weapons and materials. A communique has been issued, saying the threat of nuclear and radiological terrorism remains one of the greatest challenges to international security. It said more needs to be done to prevent non-state actors from obtaining nuclear and other radioactive materials.

WASHINGTON D.C., April 1, 2016 (Xinhua) -- Chinese President Xi Jinping (4th R, front) poses for a group photo with other leaders attending the fourth Nuclear Security Summit in Washington D.C., the United States, April 1, 2016. (Xinhua/Xie Huanchi)

At the closing news conference, US President Barack Obama made a push for increased intelligence-sharing to prevent terror strikes. He said a lot of nuclear material needs to be secured.

"Nevertheless, as I said earlier, our work is by no means finished. There's still a great deal of nuclear and radioactive material around the world that needs to be secured. Global stocks of plutonium are growing, nuclear arsenals are expanding in some countries, with more small tactical nuclear weapons which could be at greater risk of theft," Obama said.