The PSNI has said it believes Chief Constable George Hamilton's Twitter account may have been hacked on Thursday.
The police said a tweet was posted on the account earlier.
The message contained a person's name followed by a jumble of letters.
"At this time we believe there is a possibility the account was maliciously hacked," Det Chief Insp Michael Harvey, the head of the PSNI cyber crime centre, said.
"Inquires are currently ongoing. There are no further details at this time."