WASHINGTON – President Donald Trump opened another week of impeachment turmoil with slashing attacks on his accusers – including a suggestion that a leading investigator be arrested for "treason."

Claiming that Rep. Adam Schiff, D-Calif., chairman of the House Intelligence Committee, falsely described his phone call with the president of Ukraine, Trump tweeted Monday, "Arrest for Treason?"

Schiff did not immediately respond, but others called it an outrageous comment.

"Out. Of. Control," Republican strategist Mike Murphy tweeted. "Treason? A POTUS saying this? #UnfitAndUnstable."

Alleged "treason" was part of a series of tweets Sunday night and Monday morning in which Trump raised the specter of "civil war," said some of his own aides may be "SPYING" on him and accused the Democrats of trying to "destabilize" the country before his 2020 fight for reelection.

"They are lying & cheating like never before in our Country’s history in order to destabilize the United States of America & it’s upcoming 2020 Election," Trump said.

"If the Democrats are successful in removing the President from office (which they will never be), it will cause a Civil War like fracture in this Nation from which our Country will never heal,'" Trump quoted Baptist pastor Robert Jeffress as saying.

That tweet drew criticism from Rep. Adam Kinzinger, R-Ill.

"I have visited nations ravaged by civil war.@realDonaldTrump," Kinzinger tweeted. "I have never imagined such a quote to be repeated by a President. This is beyond repugnant."

House Democrats are investigating allegations that Trump tried to coerce the president of Ukraine into investigating an American political rival, Democratic presidential candidate Joe Biden.

"We had no choice but to move forward with an impeachment inquiry," Schiff tweeted Sunday. "And our focus will be on the president’s fundamental breach of his oath office."

He added, "Coercing a foreign nation to interfere in our election is never ok, No matter what the president and his defenders say."

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Accusing the Intelligence Committee chairman of misrepresenting his conversation with the president of Ukraine, Trump tweeted, "I want Schiff questioned at the highest level for Fraud & Treason."

Trump demanded to know the identity of the unnamed whistleblower whose complaint triggered the investigation – as well as the name of any administration official who fed information to the whistleblower about his interactions with foreign leaders.

"Was this person SPYING on the U.S. President?" Trump said. "Big Consequences!"

Monday morning, he tweeted that he is again being subjected to a "witch hunt" and claimed that "the Fake Whistleblower complaint is not holding up."

As the presidential offensive continues, the White House is preparing a defense against the impeachment investigation.