Washington, Jan 16 (IANS): The US Department of Justice's (DOJ) Office of the Inspector General announced that it will launch an investigation into violent protests staged by supporters of outgoing President Donald Trump at the Capitol building on January 6.

The Office said in a statement on Friday that it will initiate a review "to examine the role and activity of DOJ and its components in preparing for and responding to the events at the US Capitol on January 6, 2021", Xinhua news agency reported.

The investigation will be led by Inspector General Michael Horowitz.

It will involve efforts from the Department of Defense, the Department of Homeland Security and the Department of the Interior, and assess whether information of potential violence was shared by the DOJ to other agencies, including the Capitol Police, which was criticised for insufficient preparation for the riot that left five people, including a Capitol Police officer, dead.

The probe will also "assess whether there are any weaknesses in DOJ protocols, policies, or procedures that adversely affected the ability of DOJ or its components to prepare effectively for and respond to the events at the US Capitol on January 6", the statement said.

The Washington Post first reported on Tuesday that the Federal Bureau of Investigation's (FBI) office in Norfolk, Virginia, explicitly warned of violent extremists planning a "war" in Washington, D.C., on January 6 to stop the certification of President-elect Joe Biden's election victory at Congress.

The warning was issued on January 5, contradicting "a senior official's declaration the bureau had no intelligence" of harmful conducts by supporters of President Donald Trump in advance, the Post said.

"As of 5 January 2021, FBI Norfolk received information indicating calls for violence in response to 'unlawful lockdowns' to begin on 6 January 2021 in Washington, D.C.," the Post cited the document as saying.

"An online thread discussed specific calls for violence to include stating 'Be ready to fight. Congress needs to hear glass breaking, doors being kicked in, and blood from their BLM and Pantifa slave soldiers being spilled. Get violent. Stop calling this a march, or rally, or a protest. Go there ready for war. We get our President or we die. Nothing else will achieve this goal'," the newspaper report added.

FBI Director Christopher Wray said Thursday in his first public appearance since the riot that his agency has identified over 200 suspects, and that more than 100 arrests have been made to date.

The FBI has issued a warning about plans of armed protests from January 16 through January 20 at all the 50 state capitols, and from January 17 through January 20, the day of the inauguration, at the Capitol in Washington D.C.

At least 20,000 National Guard troops are expected to be deployed in Washington D.C.