WASHINGTON - Twitter permanently suspended President Donald Trump's account on Friday (Jan 8) due to "the risk of further violence", two days after it temporarily locked him out and warned that he would be banned for good if he continued to incite violence and share false claims of electoral fraud.

The ban was part of the deepening fallout from Wednesday's mob attack on the Capitol, which many in Washington saw as having been incited by Mr Trump, as Congress was certifying President-elect Joe Biden's victory.

Mr Trump slammed the ban in a statement to the media and said he would have a big announcement soon, adding that Twitter had "gone further and further in banning free speech" and was in cahoots with the "radical left".

"Tonight, Twitter employees coordinated with the Democrats and the Radical Left in removing my account from their platform, to silence me - and YOU, the 75,000,000 great patriots who voted for me," said Mr Trump.

He added that he had been negotiating with various other sites, without naming any, and that he would also look into building his own platform in the near future.

Mr Trump had initially posted the statement on the official government account @POTUS, but it was quickly deleted by Twitter.

His son, Mr Donald Trump Jr, protested his father's ban on his own account, writing: "Free-speech no longer exists in America."

In a statement explaining its ban, Twitter said that two of Mr Trump's tweets were highly likely to encourage and inspire people to copy Wednesday's violence at the Capitol.

It warned that plans for future armed protests had already begun proliferating on Twitter and off it. These include a proposed secondary attack on the US Capitol and state capitol buildings on Jan 17, three days before Mr Biden's inauguration.

The first of Mr Trump's offending tweets had been posted on Friday. He wrote: "The 75,000,000 great American Patriots who voted for me, AMERICA FIRST, and MAKE AMERICA GREAT AGAIN, will have a GIANT VOICE long into the future. They will not be disrespected or treated unfairly in any way, shape or form!!!"

Twitter said that the use of the words "American Patriots" to describe some of his supporters was being interpreted as "support for those committing violent acts at the US Capitol".

In the second offending Tweet, Mr Trump wrote he would not be attending Mr Biden's inauguration on Jan 20.

This statement was being received by a number of his supporters as further confirmation that the election was not legitimate, and a disavowal of his previous statement that there would be an orderly transition of power, said Twitter.

It "may also serve as encouragement to those potentially considering violent acts that the Inauguration would be a "safe" target, as he will not be attending", Twitter added.

Social media platforms have been grappling with how to control the spread of misinformation, calls to violence, and Mr Trump's repeated false claims of electoral fraud.

On Friday, Twitter also removed the accounts of former Trump official Michael Flynn, lawyer Sidney Powell and other QAnon conspiracy theorists, due to their "potential to lead to offline harm", a spokesman told several US media outlets.

Facebook and Instagram have also indefinitely blocked Mr Trump's accounts from posting.

Google banned the Parler app, which Trump supporters frequent and used to discuss and plan Wednesday's attack on the Capitol, on Friday. Apple has also threatened to ban it from its app store unless it moderates its content.

Meanwhile, Democrats are moving rapidly to impeach President Donald Trump for inciting his supporters to storm the Capitol on Wednesday, with media outlets reporting that formal proceedings could be launched as soon as Monday.

If Trump does not "immediately resign", the House will move forward with a motion for impeachment, House Speaker Nancy Pelosi said in a statement on Friday - with 12 days left to go until the end of Mr Trump's term.

The Republican-controlled Senate is unlikely to vote to convict Mr Trump, a feat that would be logistically and politically difficult. The White House, and some Republicans, are also arguing that impeachment would further divide an already-polarised America.

Impeachment has a high chance of passing in the Democrat-controlled House, with some Republicans reportedly open to joining the effort, making this the second time Mr Trump will be impeached during his term.

He was impeached in Dec 2019 in the House for abuse of power and obstruction of Congress, but acquitted by the Republican-majority Senate.

As with last time, the Senate is unlikely to vote to remove him from office, a move that would disqualify him from holding office again.

Logistically, there may not be enough time for the Senate to hold a trial. Politically, voting to convict him would hurt vulnerable Republican senators up for reelection in 2022.

Nonetheless, more Republicans appear receptive to impeaching and convicting Mr Trump than before. Alaska senator Lisa Murkowski, one of the party's more moderate voices, became the first Republican senator to call for his resignation on Friday.

"I want him to resign. I want him out. He has caused enough damage," she told the Anchorage Daily News in an interview on Friday.

Even after Vice-President Mike Pence told Mr Trump he did not have the constitutional authority to overturn states' electoral votes, Mr Trump "still told his supporters to fight", she said.

"How are they supposed to take that? It's an order from the president. And so that's what they did. They came up and they fought and people were harmed, and injured and died," Ms Murkowsi added.

Nebraska senator Ben Sasse told CBS in a Friday interview he would "definitely consider" potential articles of impeachment, but said the question was whether impeachment would be prudent for the future of the United States.

The impeachment effort faces pushback from other Republicans, including some who voted against an attempt by their colleagues to overturn Mr Biden's electoral victory in Congress this week, who say that impeachment would be too divisive.

South Carolina senator Lindsey Graham, a Trump ally who distanced himself from the President this week, wrote on Twitter that impeachment would "do more harm than good" and "further divide the country and erode the institution of the presidency itself".

House minority leader Kevin McCarthy similarly said in a statement: "Impeaching the President with just 12 days left in his term will only divide our country more."

In a statement, the White House said: "As President Trump said yesterday, this is a time for healing and unity as one Nation. A politically motivated impeachment against a President with 12 days remaining in his term will only serve to further divide our great country."

Mr Biden declined to take sides during an event in Wilmington, Delaware, on Friday. He said: "What the Congress decides to do is for them to decide."