At least four people were killed and 52 others arrested in the wake of the violent protests that took place inside the US Capitol in Washington D.C.

Addressing the media here on Wednesday night, Metropolitan Police Department Chief Robert Contee confirmed that a woman was shot and killed, while the three others died after apparently suffering "separate medical emergencies" near the Capitol grounds, Xinhua news agency reported.

There were no other details on the victims.

Contee however, added that the woman was transported to an area hospital where she was pronounced dead.

As of 9.30 p.m. (local time) on Wednesday, the police made a total of 52 arrests, including four for carrying pistols without a license and one for possession of a prohibited weapon, The Hill news website quoted the police chief as saying.

Twenty-six of the 52 arrests were made on Capitol grounds, he added.

He also confirmed that 14 officers were injured, with one "pulled into the crowd and assaulted", resulting in "serious injuries".

According to Contee, two officers were hospitalised currently.

He said that two pipe bombs were recovered near the headquarters of the Democratic National Committee and Republican National Committee.

Also speaking at the briefing along side Contee, Washington D.C. Mayor Muriel Bowser extended an emergency declaration in the city until January 21, and imposed a curfew until 6 a.m., on Thursday morning.

Earlier Wednesday, thousands of supporters of President Donald Trump stormed the Capitol, forcing emergency evacuation at both the Senate and the House of Representatives.

The chaos unfolded as the Chambers were preparing to certify President-elect Joe Biden's Electoral College win.