The uproar has drawn comparisons to the Watergate scandal which led to the resignation of US president Richard Nixon in 1974.

Here's what we know now.

- In the days before Comey's firing, the FBI had issued subpoenas in the case of Michael Flynn, the short-lived Trump National Security Adviser who hid contacts with Russia officials and money he had received from the Russian government. Comey, who was surprised by his sacking, was seeking more resources for the investigation into collusion between people from Donald Trump's presidential campaign and Russian figures.

- Did Trump fire Comey for leading a probe into White House's Russia ties? While it appears that way, the official reason for Comey's dismissal was the handling of the Hillary Clinton email issue during the campaign. This is something Trump repeatedly praised Comey for on the campaign trial. So the timing of Comey's surprise firing looks suspicious. Trump had also reportedly grown frustrated with the negative news about his campaign's alleged coordination with Russia.

- Deputy Attorney General Rod J. Rosenstein, was reportedly directed by Trump to write the justification for Comey's sacking. Rosenstein, a career Department of Justice official, subsequently threatened to resign if the Trump White House continued to try to suggest he was the driving force behind Comey's resignation, the Washington Post reports.

- The FBI inquiry into Trump's ties with Russia should continue under the new FBI director. But there are fears that with Comey fired by Trump, the momentum behind the FBI investigations will stall.

- The Senate Intelligence Committee is continuing an investigation, even as its chairman, Republican Richard Burr said Comey's departure risks interrupting the probe. The Senate committee, which issued a subpoena seeking documents from Michael Flynn, is considered more bipartisan in spirit than the House Intelligence Committee. The House Committee's progress has been slowed after concerns its chair Congressman Devin Nunes "made unauthorised disclosures of classified information". It is now headed by Congressman Mike Conaway and is ongoing. Republican leadership in the House and Senate have both declined to created select committees with subpoena power to investigate Trump and Russia.

What now?

- The Trump White House shows no signs of cooling its relationship with Russia. The day after Comey was fired, Trump met with a Russian foreign minister Sergei Lavrov in the White House, to discuss cooperation in the Mid-East among other issues. Lavrov, when asked about Comey's firing, was dismissive.

- How likely is impeachment? Trump would need to be impeached in the House - controlled by Republicans - and tried and found guilty in the Senate - also controlled by Republicans -- to be removed from office. The threat of this happening is what saw Nixon step down in 1974 over the Watergate Scandal.

- Is this scandal like Watergate? In that event, under Nixon the White House had been converted into a covert political revenge machine replete with abuses of authority, slush funds, smear campaigns, and paid operatives. The current Trump-Russia crisis has a strong geopolitical element, with links to Russia cropping up repeatedly both in influence campaigns, hacking, but also personal contacts with figures close to Trump.

- Another difference between the US now and in the Watergate era was that in the early 1970s, Republicans and Democrats consumed largely the same media. Today, the left, right, and centre in the US are often consuming different material with vastly different perspectives and priorities. In this way, the coverage of Trump's firing of Comey may not raise the same alarm bells for conservatives who have their ear of their representatives.