US President Donald Trump has defended his dismissal of FBI Director James Comey, fighting a storm of criticism that the removal aimed at blunting a probe into his presidential campaign's possible collusion with Russia to sway the 2016 election.

The White House on Tuesday said Comey was fired over his handling of an election-year FBI probe into then-Democratic presidential nominee Hillary Clinton's use of a private email server during her time as secretary of state.

But Comey had also been leading an investigation into potential Russian collusion in last year's US presidential election.

Trump on Wednesday said Comey had lost the confidence of almost everyone in Washington and would be replaced by someone who "does a far better job".

His comments came as he welcomed Sergey Lavrov, Russia's foreign minister, to the White House in his first meeting with a Russian official since taking office on January 20.

Al Jazeera's James Bays, reporting from Washington, DC, said the timing of Comey's dismissal, in conjunction with Lavrov's visit, looked "extremely awkward" for the Trump administration.

"Here you have a president who has fired the head of the FBI, an agency that happened to be investigating associates of the president for possible collusion with the Russians over the hacking of the presidential election - and soon after that happens prominent Russians, including Lavrov and Russia's ambassador to the US, turn up in the Oval Office," Bays said.

Comey's abrupt dismissal sent shockwaves across Washington and was swiftly condemned by Democrats - as well as some in Trump's own Republican Party.

Many Democrats who had previously criticised Comey's management of the email investigation, sharply questioned the timing of his dismissal, arguing that Trump could have acted soon after taking office on January 20.

Chuck Schumer, the Senate's minority leader, called on Wednesday for the appointment of a special prosecutor to investigate alleged links between Russia and the Trump campaign.

"If there was ever a time when circumstances warranted a special prosecutor, it is right now," Schumer said.

Al Jazeera's Kimberly Halkett, reporting from Capitol Hill, said Comey's dismissal had sparked fiery reactions, mostly along party lines.

"The cries going ever louder on Capitol Hill for an investigation, but the problem is that the special prosecutor needs to be appointed by the justice department, which is controlled by the White House," she said.

Reports also emerged on Wednesday that just days before his dismissal, Comey had asked for additional funding from the justice department to expand his investigation into possible Russian election meddling.

Republicans hit back

However, Senate majority leader Republican Mitch McConnell ridiculed Democrats' criticism, saying they were "complaining about the removal of an FBI director who they themselves repeatedly and sharply criticised".

On the Senate floor, McConnell also dismissed Democratic calls for the justice department to appoint a special prosecutor for a new investigation.

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McConnell said such a move would "only serve to impede" existing probes such as one under way in the Senate intelligence committee.

For his part, Schumer called on McConnell to hold closed and potentially classified briefings with all US senators to question Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein.

The Democrat said such briefings should address why Sessions, who previously recused himself from the Russia investigation after misstating his own contacts in 2016 with Russia's ambassador to Washington, was able to influence the firing of the man conducting the FBI's Russia investigation.

"We know Director Comey was leading an investigation in(to) whether the Trump campaign colluded with the Russians, a serious offence. Were those investigations getting too close to home for the president?" Schumer said.

Vice President Mike Pence said Comey's firing was unrelated to the Russia probe.

Trump was in the process of evaluating candidates with "great integrity and great experience" to take over the FBI, Pence told reporters after meetings with lawmakers in the US Capitol.

But Republican Senator John McCain said on CNN he had not seen a "good explanation" for the firing, adding that the Clinton email investigation was not "sufficient rationale for removing the director of the FBI, and I regret that it's happened".

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US intelligence agencies concluded in a January report that Russian President Vladimir Putin had ordered an effort to disrupt the 2016 election that included hacking into Democratic Party emails and leaking them, with the aim of helping Trump.

Russia has repeatedly denied any such meddling. The Trump administration denies allegations of collusion with Russia.

Lavrov at the White House

In brief comments to the press after his meeting with Lavrov, Trump said he is seeking "mutually beneficial" and "pragmatic" relations with Moscow.

Lavrov is in Washington for a week of high-level meetings.

The uproar over Comey's dismissal complicated Lavrov's intended mission: securing US support for a Russian plan to create safe zones in war-torn Syria.

But the Russian diplomat said the two sides were seeking to "remove all the barriers" in their thorny relationship, and praised his meetings on Syria as "constructive".

"President Trump clearly confirmed his interest in building mutually beneficial, business-like pragmatic relations," Lavrov told journalists.

The Russian foreign minister dismissed claims that Moscow interfered in the election that sent Trump to the White House as "fabrications".

The Kremlin said it hoped Comey's firing would not affect Moscow's ties with Washington, saying it believed his dismissal had nothing to do with Russia.