Donald Trump released a video calling for his supporters to remain calm after the US House of Representatives voted to impeach him, as officials drastically tightened security in Washington ahead of Joe Biden’s inauguration.

“I unequivocally condemned the violence that we saw last week. Violence and vandalism have absolutely no place in our country, and no place in our movement,” Mr Trump said in the recorded message, which did not mention the House action.

“No true supporter of mine could ever endorse political violence, no true supporter of mine could ever disrespect law enforcement, or our great American flag, no true supporter of mine could ever threaten or harass their fellow Americans,” he added. “If you do any of these things, you are not supporting our movement, you’re attacking it, and you are attacking our country. We cannot tolerate it.”

The president’s appeal came after the House voted to impeach Mr Trump for an unprecedented second time on a charge of inciting a mob of his supporters who stormed the Capitol last week, resulting in five deaths.

The video reiterated the message in a brief written statement issued earlier by the White House, in which the president said: “In light of reports of more demonstrations, I urge that there must be NO violence, NO lawbreaking and NO vandalism of any kind.”

An internal intelligence bulletin issued on Monday by the US Secret Service identified several groups, including self-styled militias, as posing a potential threat to the Capitol. It warned that some of the organisers of the groups have encouraged attendees to bring weapons to events in Washington, according to a person briefed on the memo.

Before Wednesday, Mr Trump, who has been banned from Twitter since last week, had said relatively little since the assault, which grew out of demonstrations claiming that the presidential election was stolen from him. On Tuesday, he denied that anything he said to the crowd before it marched on the Capitol had been inappropriate.

Ronna McDaniel, the chair of the Republican National Committee, also called for any further protests to remain peaceful. “Anyone who has malicious intent is not welcome in Washington DC or in any other state capitol building,” she said in a statement on Wednesday.

Security in the US capital has been increased dramatically amid reports of potential security threats in the days leading up to Mr Biden’s inauguration on January 20. Many US state capitols are also tightening security.

Robert Contee, chief of the District of Columbia Metropolitan Police, said “you can expect to see somewhere upwards of 20,000” National Guard members in Washington for the inauguration. “This is a major security threat,” he said.

Members of the US National Guard have been guarding the Capitol building around the clock and were seen sleeping in its corridors ahead of the impeachment vote, marking the first time the seat of American democracy has been used as a barracks since the civil war.

A Washington DC National Guard spokesperson said personnel were given lodgings for when they were off-duty, but that the Capitol had been designated as a place where forces could rest and sleep during the 24-hour operation.

New metal detectors have also been placed at the entrance of the House chamber, which has provoked pushback from some members of Congress.

Several lawmakers have described fleeing for their lives on January 6 as pro-Trump rioters stormed their workplace while Congress moved to vote on certification of Mr Biden’s presidential election victory. Five people, including one Capitol police officer, died as a result.

The events have led to several resignations by senior officials in charge of security at the Capitol complex, and a bipartisan group of leaders across Washington called for an investigation into how law enforcement failed to stop the rioters despite multiple warnings of a potential threat.

Mr Biden received a briefing on Wednesday from the FBI, the US Secret Service, and members of his national security team on potential threats, his transition team said in a statement.

In the past week, the Department of Justice has charged more than 70 people as federal law enforcement agencies, including the FBI, said they were moving as fast as they could on an “unprecedented” investigation to catch people involved in the Capitol riot.

Among those so far arrested and charged are armed men who allegedly threatened to kill Nancy Pelosi, the speaker of the House; Muriel Bowser, the Democratic mayor of Washington; and Mr Biden. The FBI has set up a separate team to investigate threats made against journalists.

Many of those arrested have been charged with carrying illegal firearms. Prosecutors have said charges of sedition and conspiracy could be pursued.

On Wednesday, federal prosecutors in Washington said they were charging seven more people, including Robert Keith Packer, who is alleged to be the man pictured wearing a “Camp Auschwitz” sweatshirt during the riot.

Klete Keller, a former US Olympic swimmer, also faced a criminal complaint linked to the riot filed in the federal court in Washington. According to court filings, Mr Keller wore his Olympic team jacket to the riot, which appeared to have helped the FBI identify him.

Late on Wednesday evening, federal prosecutors in Washington said two off-duty Virginia police officers were among those being charged for their part in the riots.

Jacob Fracker and Thomas Robertson, both arrested on Wednesday, are being charged with entering the Capitol without authority, violent entry and disorderly conduct.

Mr Robertson is accused of bragging on social media that he was “proud” of being “willing to put skin in the game”.

US officials said they had identified about 170 people who they were investigating for potential crimes.

A spokesperson for Facebook, which has been accused of giving the rioters a platform to plan last week’s assault, said it was monitoring the situation. It has seen signals on and off the platform suggesting more potential violence is afoot, the spokesperson said.

Additional reporting by Hannah Murphy