Two days after his Attorney General recused himself from decisions on any investigation into links between Donald Trump's campaign for President and Russia, President Trump set off a new firestorm on Saturday by accusing former President Barack Obama of wiretapping Mr. Trump's phone conversations in 2016, as members of both parties called for the President to provide evidence to back up his charge.

"We are in the midst of a civilization-warping crisis of public trust," said Sen. Ben Sasse (R-NE). "The President today made some very serious allegations, and the informed citizens that a republic requires deserve more information."

"This allegation has serious implications," said Rep. Justin Amash (R-MI), who has been a frequent critic of the new President.

"I'm very worried," Sen. Lindsey Graham (R-SC) said at a town hall meeting in his home state, again urging that details be made public about the President's charge.

Other than Graham, Sasse and Amash, most Republicans in the Congress simply stayed silent on Saturday about Mr. Trump's early morning tweets, which claimed that he had been the target of wiretaps, directly approved by ex-President Obama.

"This is McCarthyism!" Mr. Trump tweeted early in the morning from his Mar-a-Lago retreat in Palm Beach, Florida, as the President offered no evidence to explain why the FBI would have wiretapped his phone.

The Saturday morning Twitter blast came after what several news organizations said was an Oval Office outburst directed by the President at his senior staff on Friday, reportedly angry about the move by Attorney General Jeff Sessions to recuse himself from any probe related to Russia.

On the road in Virginia on Thursday afternoon, the President had told reporters that he saw no need for Sessions to recuse himself; not long after, the Attorney General announced exactly that.

More than 12 hours after Mr. Trump's tweets, there still had been no official comment from the White House; the President spent part of his day at one of his golf courses in Florida, and was having dinner with several of his Cabinet secretaries.

As for Democrats, they used the latest outburst by the President to demand a special counsel probe of any links between Russia and the Trump campaign.