Democrats have asked ousted FBI Director James Comey to testify on Capitol Hill, a day after he was fired by Donald Trump.

Reports said Senate Intelligence Committee chairman Richard Burr, a Republican, and Democrat ranking member Mark Warner, said they had asked Mr Comey to appear before the committee next Tuesday.

It was not immediately clear whether Mr Comey would accept the invitation, or if the testimony would be public or closed.

"[We sent out the invitation. We've not heard back yet, we just sent out the invitation this morning," he said, according to CNBC.

“He was due to appear tomorrow with all the other heads of the intelligence community. My hope is that he’ll take advantage of this opportunity.” 

News of the invitation came as Mr Trump defended his decision to get rid of Mr Comey, a move that was widely criticised by Democrats and at least a dozen Republicans. 

Mr Trump said that the FBI Director “was not doing a good job”. The president did not explain more about the manner and timing of Mr Comey’s ousting.

Mr Warner, along with many of his Democratic colleagues, has called for a special counsel in the Russia probe. 

Mr Comey reportedly found out that he had been fired on Tuesday around the time the news broke on television.

Mr Trump, who received recommendations to fire Comey from Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein, wrote in a letter that he wanted to to “find new leadership for the FBI that restores public trust and confidence in its vital law enforcement mission”.

“The president over the last several months lost confidence in Director Comey, the DOJ (Department of Justice) lost confidence in Director Comey, bipartisan members of Congress made it clear that they had lost confidence in Director Comey and most importantly the rank and file of the FBI had lost confidence in their director,” Deputy White House Press Secretary Sarah Huckabee Sanders told a briefing.