President Trump, in a Saturday morning tweetstorm, responded to the mounting questions over his ties to Russia by accusing then-President Obama of wiretapping him at Trump Tower just before the November election — an accusation an Obama spokesman denied.

The unsubstantiated outburst follows several days of stories raising questions about meetings between members of the Trump campaign and Russian officials, particularly two previously undisclosed meetings between now Attorney General Jeff Sessions and Russian ambassador Sergei Kislyak.

"How low has President Obama gone to tapp [sic] my phones during the very sacred election process," he writes. "This is Nixon/Watergate. Bad (or sick) guy!"

Kevin Lewis, Obama's spokesman, said in a statement: "A cardinal rule of the Obama Administration was that no White House official ever interfered with any independent investigation led by the Department of Justice.

"As part of that practice, neither President Obama nor any White House official ever ordered surveillance on any U.S. citizen," he said. "Any suggestion otherwise is simply false."