Image copyright AFP/Getty Images Image caption The National Mall is located in central Washington DC

A man who planned to blow himself up in Washington DC on the day of next month's mid-term elections has been held and charged, US prosecutors say.

They say Paul Rosenfeld, 56, built a 200lb (91kg) explosive device and wanted to detonate it on the National Mall in the capital on 6 November.

They say he wanted to draw attention to his belief in "sortition" - a political theory that advocates the random selection of government officials.

He could be jailed for 20 years.

'Untold destruction' threat

Mr Rosenfeld - who waived his right to remain silent - was charged with two counts of manufacturing and transporting explosives on Wednesday, the prosecutors say.

"Had he been successful, Rosenfeld's alleged plot could have claimed the lives of innocent bystanders and caused untold destruction," said Assistant Director-in-Charge William Sweeney of the New York Office of the Federal Bureau of Investigation (FBI).

"Fortunately, his plans were thwarted by the quick action of a concerned citizen and the diligent work of a host of our law enforcement partners and the FBI's Joint Terrorism Task Force," he added.

Law enforcement agents say the huge explosive device was found at the suspect's home in Tappan, New York state, on 9 October.

This came after an individual had received letters and text messages from the suspect about the plot, and had alerted the authorities.

Mr Rosenfeld later admitted that he had ordered large quantities of black powder, an explosive substance, on the internet and had conducted test detonations, the prosecutors say.