Comey’s ouster has raised urgent questions over the future of the FBI probe into what US intelligence has called Russian meddling in the 2016 election, and possible collusion between the Kremlin and Trump’s team.

With tensions running high on Capitol Hill, the Democratic opposition called for the Justice Department to appoint a so-called special counsel to oversee the investigation.

Senate Majority Leader Mitch McConnell rejected that suggestion.

“Today we will no doubt hear calls for a new investigation which could only serve to impede the current work being done,” McConnell told the chamber.

Comey was officially sacked for mishandling a high-stakes probe into the emails of Trump’s presidential rival, Hillary Clinton.

But the White House explanation was greeted with overwhelming skepticism from Democrats, and some Republicans.

Top Senate Democrat Chuck Schumer, leading calls for a special counsel, said there was “little reason to think” it was the true reason Trump fired Comey.

“We know director Comey was leading an investigation into whether the Trump campaign colluded with the Russians,” Schumer said. “Were those investigations getting too close to home for the president?”

Republicans seeking to steady a listing ship focused on some of their more prominent priorities, notably health care.

But the Comey crisis has rocked Capitol Hill. Newly installed acting FBI director Andrew McCabe testifies Thursday in an open hearing before the Senate Intelligence Committee, one of three Senate panels investigating the Russia allegations.

And committee aides confirmed that Comey has been invited to testify Tuesday in a closed-door session.

– Subpoena issued -In a sharp new development in the Russia probe, the Senate Intelligence Committee announced Wednesday it issued a subpoena to Trump’s former national security adviser Michael Flynn for Russia-related documents.

The committee said in a statement that it “first requested these documents in an April 28, 2017 letter to Lieutenant General Flynn, but he declined, through counsel, to cooperate.”

Flynn was sacked after lying to Vice President Mike Pence about his discussions with the Russian ambassador to Washington, leaving him vulnerable to leverage from Moscow.

Senate Intelligence Committee chairman Richard Burr told reporters he did not feel an independent inquiry was necessary.

Even though the timing and reasoning of Comey’s firing “doesn’t make sense to me,” he said, he was proceeding with the committee probe.

“I hope to do it in a bipartisan way, but the investigation will run its course,” Burr said.

Schumer signaled his anger with McConnell’s refusal to back an independent special prosecutor by giving the green light to a Democratic work slowdown, which drew on an obscure Senate rule that bars committee hearings from operating beyond mid-day.

Democrats threw up another hurdle when Senator Ron Wyden announced a “hold” on a US Treasury nomination until the department provides documents related to Russia and its financial dealings with Trump.

Senate Democrat Richard Blumenthal suggested another far more consequential tactic, as he indicated he would vote against any new FBI director nominee “until there was support for a special prosecutor.”

Several Republicans meanwhile joined Democrats in expressing concern about the details of Comey’s dismissal.

Senate Republican John McCain said he has long-backed a “special congressional committee,” while moderate Republicans Susan Collins and Lisa Murkowski said they were studying the option.

“There’s no question that we are in a very volatile, sensitive and fragile time in this nation,” Senator Tim Scott said.

“The White House’s timing of the firing was less than impeccable,” added fellow Republican Senator John Kennedy. DM