An embattled Donald Trump complained Wednesday that no US leader had been treated “more unfairly,” as top Republican lawmakers demanded the facts on the swirling scandals convulsing his presidency.

The White House has been thrown into turmoil by a succession of stunning allegations against the president, most damagingly the suggestion he may have obstructed justice by asking his FBI chief to drop a probe into one of his top advisors.

“We need the facts,” House Speaker Paul Ryan, the top Republican in Congress, told reporters in reaction to the explosive reports of Trump's request to the now-sacked James Comey, coming on the heels of claims he shared US secrets with Russian officials in the Oval Office.

“It is obvious there are some people out there who want to harm the president. But we have an obligation to carry out our oversight regardless of which party is in the White House,” Ryan added.

Trump remained uncharacteristically quiet early Wednesday on Twitter, his favored platform for reaching his base. But by midday, during a commencement address at the US Coast Guard Academy, he was venting his frustration.

“No politician in history, and I say this with great surety, has been treated worse or more unfairly,” he said. “You can't let them get you down.” Trump urged graduating cadets to follow his example and “fight, fight, fight. Never, ever, give up,” assuring them: “Things will work out just fine.”

Comey summoned

On Capitol Hill however, some Republicans have begun siding with the many Democrats who are demanding an independent investigation to get to the bottom of a series of issues, including the Trump team's possible connections with Moscow.

That could come either through the appointment of a special prosecutor, or the creation of a congressional commission — two moves the Republican leadership has so far resisted.

In the meantime, though, the Republican chairman of the House Oversight Committee, Jason Chaffetz, said Tuesday night he was prepared to subpoena the memo in which Comey reportedly recounted his talk with Trump.

In a letter to acting FBI director Andrew McCabe, Chaffetz demanded the bureau turn over “all memoranda, notes, summaries, and recordings referring to or relating to any communications between Comey and the president” by next Wednesday.

The Republican head of the Senate Intelligence Committee, Richard Burr, went further by requesting Comey himself appear before the panel “in both open and closed sessions.”

Putin's helping hand

In a further, extraordinary twist to developments, President Vladimir Putin waded in to say Moscow could provide Congress with a record of Trump's controversial exchange with Russia's top diplomat and its ambassador to Moscow last week.

Putin caused a stir by using the Russian word for audio recording, but his foreign policy aide Yuri Ushakov subsequently clarified that “audio is not made” at such meetings, and that he was referring to a written record The Washington Post reported Monday that Trump had shared highly-classified intelligence about an Islamic State group terror threat — divulging secrets provided by a third party in a major breach of intelligence protocol.

A US administration official confirmed to AFP on condition of anonymity that the original intelligence came from Israel, news that cast a shadow over the US president's visit to the country next week.

The Russian leader also mocked the idea that Trump had shared secrets during the Oval Office meeting, calling the allegations “political schizophrenia” spread by people who were either “dumb” or “corrupt.” US lawmakers swiftly shot down the prospect of Putin providing evidence to an American congressional investigations, with Senator Susan Collins dismissing the notion as “absurd.”

'Right the ship'

Collins however is among a growing number of Republicans, including Senator John McCain and congressman Adam Kinzinger, who are deeply troubled by the latest White House scandals, and how a party that helped sweep Trump into office may now have to sit in judgment of the president.

“He needs to right the ship,” Collins, a moderate, told Newsradio WGAN. “We cannot have this constant chaos and serious questions being raised virtually every single day.” Kinzinger added on CNN: “I think we're at the position now where it is time for an independent commission or a special prosecutor.” Other Republicans were still standing by their man.

“Let's let Congress do its job, and let's not panic here,” congressman James Comer told reporters. “This is a new administration. I think the president deserves a chance.”

The fresh US crisis sank the dollar as well as Hong Kong stocks amid worries that Trump's economy-boosting and tax-cutting agenda could be derailed, as both analysts and handful of lawmakers on Capitol Hill began openly to raise the prospect of a possible impeachment.