Trump accused of asking FBI to end Michael Flynn investigation

US President Donald Trump asked then-FBI director James Comey to end the agency's investigation into ties between former White House national security adviser Michael Flynn and Russia, according to a source who has seen a memo written by Comey.

According to the memo, Trump reportedly told Comey: "I hope you can see your way clear to letting this go, to letting Flynn go. He is a good guy, I hope you can let this go," after a White House meeting in February.

The memo was written immediately after the meeting, a day after Michael Flynn resigned for misleading Vice President Mike Pence about the extent of his conversations last year with Russia's ambassador, Sergei Kislyak.

The Comey memo, first reported by the New York Times, caused alarm on Capitol Hill and raised questions about whether Trump tried to interfere with a federal investigation.

In a letter to acting FBI director Andrew McCabe, the Senate Oversight Committee demanded that all memos and other documents or recordings relating to communications between Trump and Comey be turned over by 24 May.

"If true, these memoranda raise questions as to whether the president attempted to influence or impede the FBI's investigation as it relates to Lieutenant General Flynn," wrote committee Chairman Jason Chaffetz, a Republican.

The new development followed a week of tumult at the White House after Trump fired Comey and then discussed sensitive national security information about Islamic State with Russian Foreign Minister Sergei Lavrov.