U.S. President Donald Trump has accused his predecessor, Barack Obama, of wiretapping his New York office during the election campaign, but has not provided evidence of the charge.
"Terrible! Just found out that Obama had my 'wires tapped' in Trump Tower just before the [election] victory. Nothing found. This is McCarthyism!" Trump wrote on Twitter on March 4.
The tweet was followed within minutes by three more Twitter posts in which Trump asserted without evidence that Obama had his phone calls intercepted and monitored.
"How low has President Obama gone to tapp [sic] my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!" one of the tweets said, in reference to the 1972 wiretapping of the Democratic National Committee headquarters in Washington which led eventually to Republican President Richard Nixon's resignation in 1974.
Several hours later, Obama spokesman Kevin Lewis categorically denied Trump's claims.
"Neither President Obama nor any White House official ever ordered surveillance of any U.S. citizen," Lewis said. "Any suggestion otherwise is simply false."
He also said it was a "cardinal rule" of the Obama administration never to interfere in "any independent investigation of the Department of Justice."
Trump's tweets come as his administration once again faces questions over the presidential campaign team's contacts with Russia prior to Trump's inauguration.
Trump's first address to Congress this week was quickly overshadowed by the revelation that Attorney General Jeff Sessions -- one of Trump's earliest supporters -- had met twice with the Russian ambassador.
Sessions never disclosed the encounters during his Senate confirmation hearings, despite direct questions on the subject.
The president defended Sessions on Twitter, saying that one of the meetings was arranged by an educational program run by the State Department.
Trump is spending the weekend at his Mar-A-Lago residence in Palm Beach, Florida. It is his fourth visit there since he was inaugurated in January.