A small aircraft known as a gyrocopter has landed on the west lawn of the US Capitol building.
The operator of the aircraft has been arrested by Capitol police.
The Tampa Bay Times tells the BBC the driver is Doug Hughes, a Florida post man who wanted to deliver a message about campaign finance reform to Congress.
The airspace around the Capitol and White House in Washington DC is restricted to official aircraft.
US Capitol police said they continued “to investigate with one person detained and temporary street closures in the immediate area”.
Emergency vehicle rushed to the area and a robot bomb detector was sent over to the gyrocopter.
Mr Hughes apparently left for the Washington DC area from his home in Ruskin, Florida, last week with his gyrocopter, the Tampa Bay Times wrote.
His intention, the paper said, was delivering letters urging members of Congress to reform the US political financial system.
Representative Michael McCaul, chairman of the House homeland security committee, said that had he made it much closer to the Capitol, officials were prepared to shoot him down.