The world needs to do more to prevent "nuclear terrorism", the head of the UN atomic watchdog said ahead of a summit next week and in the wake of the Brussels terror attacks.

"Terrorism is spreading and the possibility of using nuclear material cannot be excluded," International Atomic Energy Agency (IAEA) chief Yukiya Amano told AFP in an interview.

"Member states need to have sustained interest in strengthening nuclear security," he said. "The countries which do not recognise the danger of nuclear terrorism is the biggest problem."