Protesting mailman lands helicopter on Capitol lawn

An anti-corruption protester has flown a mini helicopter through Washington's no-fly zone and landed it on the US Capitol lawn, triggering a national security scare and prompting a police probe.

“The US Capitol Police continues to investigate, with one person detained and temporary street closures in the immediate area,” USCP officer Shennell Antrobus told AFP.

The pilot, according to the Tampa Bay Times who had interviewed and filmed him prior to his audacious flight, is a Florida man who was conducting civil disobedience - in this case, a demand for campaign finance reform.

A Florida postal carrier named Doug Hughes took responsibility for the stunt on a website where he said he was delivering letters to all 535 members of Congress in order to draw attention to campaign finance corruption.

The mini helicopter, right, about to land on the Capitol lawn. Picture: AP

Air space is severely restricted around Washington landmarks including the White House and the Capitol, which houses the US Congress, whose 535 lawmakers were in session at the time.

A bomb squad inspected the so-called gyrocopter, which landed a few hundred metres from the Capitol, but found nothing hazardous.

Authorities reportedly put the building on temporary lockdown although it was not evacuated.

Iraq's Prime Minister Haider al-Abadi was in the Capitol at the time for a meeting with senators.

The breach, during a high-volume tourist season, was the second major air security scare this year in the capital.

bomb squad officer with the gyrocopte. Picture: James Borchuck/Tampa Bay Times/Zuma Press/TNS

In January, an intelligence agency employee lost control of a hobby drone and crashed it into the White House gardens, sparking a Secret Service investigation.

President Barack Obama has been briefed about Wednesday's incident, the White House says.