I'd bet a good lawyer could make a great case out of the fact that President Obama was tapping my phones in October, just prior to Election!- Donald J. Trump (@realDonaldTrump) March 4, 2017
Mr Trump leveled the charges in a flurry of tweets shortly after dawn, amid an avalanche of recent revelations about communications between Russian officials and some of his senior aides, including Attorney General Jeff Sessions.
How low has President Obama gone to tapp my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!- Donald J. Trump (@realDonaldTrump) March 4, 2017
Mr Trump repeatedly has denied having any personal ties to the Kremlin, and his aides have denied or played down contacts with Russian officials.
But the accusations have continued amid almost daily leaks to the press that have revealed new details about links between Moscow and senior Trump officials.
One such revelation earlier this week in the Washington Post about a meeting between Sessions and Russian Ambassador Sergey Kislyak prompted the Republican former US senator to recuse himself from any investigations into the Trump campaign's possible Russia ties.
Mr Sessions had told a Senate committee under oath that he "did not have communications with the Russians," but reporters found that he had actually met the Russian ambassador twice in the months before taking up his post as attorney general, America's top law enforcement officer.
Mr Trump has expressed his displeasure over the charges - and the barrage of leaks that led to them - lashing out in tweets Friday directed at the top Democrats in the Republican-led Congress - Senator Chuck Schumer and Representative Nancy Pelosi.
The businessman-turned-politician, who has accused his political foes of conducting "a total witch hunt" on Saturday directed his Twitter tirade at his Democratic predecessor.
"Terrible! Just found out that Obama had my 'wires tapped' in Trump Tower just before the victory. Nothing found. This is McCarthyism!" Mr Trump wrote a day after departing Washington for a weekend getaway at his Mar-a-Lago Florida resort for the fourth time in five weeks.
Since US intelligence took the unprecedented step of publicly accusing Russia of trying to swing the November election in Mr Trump's favor, questions have swirled about whether some in Mr Trump's campaign colluded with Moscow.
But it has now emerged that a slew of associates aside from Sessions and already fired national security advisor Michael Flynn met Kislyak before Mr Trump took office.
The meetings have raised red flags for Democrats, who have called for Mr Sessions to resign and be investigated for perjury.