A Capitol Hill policeman became the fifth person to be killed after protesters pro-Trump rioted in US congress.

Sources familiar with the matter confirmed the information on January 7, saying that the officer was hit in the head by a demonstrator using a fire extinguisher in the head.

This is the fifth person killed in the riots on January 6, when the US Congress held a meeting to confirm the results of the election.

One woman was shot dead on the spot by Capitol Hill police, and three others died in hospital after being rescued.

In his first statement about the riots, Capitol Hill police chief Steven Sund denounced the crowd for "aggressively attacking" police defending parliament building and law enforcement officers with metal pipes, chemicals.

Congressmen said the security forces lacked meticulous standards, although Trump has called for a large demonstration for weeks to prevent Congress from confirming Joe Biden's victory.

However, Mr. Sund explained that the police were planning a free speech demonstration without anticipating the violent attack.

Sun announced it would resign on January 16 at the call of House Speaker Nancy Pelosi.