Terrorist organisation Al-Qaeda has attempted to buy nuclear material from the former Soviet Union and Europe.

But it was cheated several times by criminal organisations. Osama bin Laden once paid US$1 million to buy a uranium canister. But when he tested it in Khartoum, Sudan, for radiation levels, he discovered that it did not contain uranium, a material used to make nuclear bombs.

The present Al-Qaeda leader Ayman al-Zawahiri is keen to acquire nuclear material. In 2001, he claimed that his organisation had bought nuclear material from the black market. Nuclear terrorism expert Professor Rajesh Basrur watches these developments closely.

He also looks at why terrorist groups have not launched any nuclear attacks. Al-Qaeda's inability to acquire sufficient material to make nuclear weapons could be one reason, says Prof Rajesh, 60, from the S. Rajaratnam School of International Studies.

Or the terrorists might be waiting for an opportunity to carry out such a catastrophic attack, he says.

Although Singapore does not have nuclear power, it plays an important role in preventing nuclear material from falling into the wrong hands, he notes.The country is also vulnerable, since it could be exposed to dangerous radiation if a nuclear attack occurred elsewhere in the region. As one of the world's busiest ports, Singapore has measures to ensure that radioactive materials found in container cargo are identified and neutralised.

Singapore also tries to ensure that nuclear material and technology meant for peaceful purposes are not used in ways that could threaten regional and international peace and stability.

Read the full interview with Prof Rajesh in The Straits Times on Saturday, March 22, 2014.