WASHINGTON, United States (AFP) — A Congressional committee will investigate President Donald Trump’s claim that Barack Obama tapped his phone during last year’s election campaign, the panel’s chairman said Sunday.

The House Permanent Select Committee on Intelligence has been examining Russian interference in last year’s US presidential election.

Devin Nunes, a California Republican who chairs the committee, said in a statement that the investigation involves looking at “the US government’s response to actions taken by Russian intelligence agents during the presidential campaign.”

“The Committee will make inquiries into whether the government was conducting surveillance activities on any political party’s campaign officials or surrogates,” he said, without specifically referring to Trump’s explosive accusation.

Trump made his allegation in a string of tweets early Saturday morning, at one point calling former president Obama a “Bad (or sick) guy!” He did not provide any evidence to back up his claims.

The White House on Sunday called on Congress to follow up on Trump’s claims.

Obama, via a spokesman, has denied any allegation of wiretapping as “simply false.”

Obama’s director of national intelligence James Clapper told NBC on Sunday that there was “no such wiretap activity mounted against the president-elect at the time as a candidate or against his campaign.”