On average every two days we receive new information of an incident involving theft or smuggling of nuclear material."
UK Foreign Secretary David Miliband said that nuclear nations like Pakistan were vulnerable.
A senior American counter-terrorism expert, John Brennan, warned that al-Qaeda had been seeking material for a nuclear bomb for more than 15 years.
"There have been numerous reports over the past eight or nine years of attempts to obtain various types of purported material," he told reporters.
"We know al-Qaeda has been involved a number of times. We know they have been scammed a number of times."
