US President Donald Trump has accused his predecessor of wire-tapping his phone a month before he was elected.
President Trump tweeted early on Saturday: "Terrible! Just found out that Obama had my "wires tapped" in Trump Tower just before the victory. Nothing found. This is McCarthyism!"
He went on to say that a court had earlier denied a wiretap request.
The US president has given no details to back up the claim - or suggested which court order he was referring to.
Media reports in the last few weeks have suggested the FBI had sought a warrant from the foreign intelligence surveillance court (Fisa) last summer in order to monitor members of the Trump team suspected of irregular contacts with Russian officials.