­The US woke up on Thursday to a “triple whammy” of new media reports linking the Trump administration with Russia, throwing the White House on the defensive and sparking fresh calls for a formal investigation.

Mr Sessions has issued fresh denials that he spoke to Russian officials to discuss the elections.

He told NBC News the reports were “unbelievable”, adding that he would only recuse himself from an investigation into Russian involvement in the election “whenever it’s appropriate” to do so.

Jeff Sessions says under oath that he has not had any contact with Russia

The Justice Department does not deny Mr Sessions met the ambassador in July and September 2016, but says that he did so in his capacity as a member of the Senate Armed Forces committee and not to discuss the election.

The Attorney General was an early supporter of Mr Trump as a Republican candidate and served as a policy adviser during his campaign. The Justice Department says he had more than 25 conversations with foreign ambassadors last year, including two with Russia’s Sergey Kislyak, in his capacity as a senior member of the Senate Armed Services Committee.

But he failed to mention this contact in his confirmation hearing in January when asked what he would do if “anyone affiliated” with the Trump campaign had been in contact with the Russian government, and House minority leader Nancy Pelosi said this amounted to “lying under oath”.

Justice Department spokeswoman Sarah Isgur Flores insisted on Wednesday night that “there was absolutely nothing misleading about his answer”. Some Democrats have said the omission is grounds enough for Sessions to be relieved of his post, while Adam Schiff, the top Democrat on the House Intelligence Committee, said Mr Sessions “must” now recuse himself of any role investigating Trump campaign ties to Russia.

The Washington Post’s report was followed up by one in the Wall Street Journal, quoting sources as saying US investigators have already started examining contacts between Mr Sessions and Russian officials during the presidential campaign.

Whether that inquiry was still going on, and what its findings were, wasn’t clear, the sources said.

The newspaper reported that the FBI had been leading the investigation, which was part of a wide-ranging probe by the intelligence services into communications between Trump surrogates and Russian operatives.

And separately, the New York Times reported that meetings took place during the election in multiple European cities, between Russian officials and associates of Mr Trump.

It cited three former American officials, and said the meetings had been monitored by the British and Dutch intelligence services who then in turn notified the US government under Barack Obama.

American spies had also intercepted Russian communications in which officials, including some with the Kremlin, discussed contacts with the Trump team, the Times reported.

Mr Trump has denied having any knowledge that aides were in touch with Russian intelligence agents during the election, and such denials prompted Obama-era officials to rush to preserve any evidence to the contrary, according to the Times.

On Tuesday, White House lawyers instructed the president's aides to preserve any materials that could be connected to Russian interference in the election, three administration officials told the Associated Press.

The Senate intelligence committee, which is investigating Russia's role in the 2016 election, has also asked more than a dozen organisations, agencies and individuals to preserve relevant records.

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The three administration officials who confirmed that White House staffers were instructed to comply did so on the condition of anonymity because they were not authorised to publicly disclose the memo from White House counsel Don McGahn.

One official said McGahn's memo instructs White House staff to preserve material from Trump's time in office, and for those who worked on the campaign, relevant material from the election.