Homeland Security and Energy department leaders urge cities vulnerable to terrorism to undergo an inventory of all radioactive material within city limits, so authorities can detect "dirty bombs" terrorists might plant.

Beset by delays, cost overruns and technical problems, the U.S. government's quest to defend the nation against a smuggled nuclear weapon or radiological "dirty" bomb is approaching a crossroads.

The US is set to begin deploying a new generation of radiation detectors intended to be America's "last line of defense" against weapons of mass destruction.

The potential for a radiological attack on the United States continues to receive less attention in Washington than nuclear, biological and chemical threats, despite a widely held view that a radiological attack is more likely than the others, according to experts.

A smart phone that can detect radiation may soon be helping the police to find the raw materials for radioactive ?dirty bombs? before they are deployed. The phones will glean data as the officers carrying them go about their daily business, and the information will be used to draw up maps of radiation that will expose illicit stores of nuclear material.

The risk of somebody somewhere triggering a radioactive "dirty bomb" is growing, evidence gathered by the UN's International Atomic Energy Agency suggests.

Concerns are growing that Al Qaeda or a related group could detonate a "dirty bomb" that would spew radioactive fallout across an American or European city, according to intelligence analysts, diplomats and independent nuclear experts.

Potential deaths and decontamination costs tied to "dirty bombs" ? conventional explosives laced with radioactive materials ? have been underestimated, a prominent researcher says.

The United States is ill prepared to deal with the long term aftermath of a 'dirty-bomb' terrorist attack, say analysts. They warn that existing clean-up laws and regulations covering radioactive materials were not designed with dirty bombs in mind, and give conflicting recommendations.

The large amount of radioactive material used India and Pakistan have led to concerns of a possible radiological, or even nuclear, terrorist incident in the region, according to a report released this month by the Henry L. Stimson Center.