Britain's Foreign Office is criticizing "childish" pranksters who called Foreign Secretary Boris Johnson posing as the leader of Armenia.

The Guardian newspaper says Johnson was called by Russian duo Alexei Stolyarov and Vladimir Kuznetsov, known as Lexus and Vovan.

One pretended to be Armenian Prime Minister Nikol Pashinian, and the newspaper says Johnson spoke to them for 18 minutes, discussing topics including the poisoning of ex-spy Sergei Skripal.

The Foreign Office said Thursday that Johnson "realized it was a hoax, and ended the call. We checked it out and knew immediately it was a prank call."

It says "the use of chemical weapons in Salisbury and Syria and recent events in Armenia are serious matters. These childish actions show the lack of seriousness of the caller and those behind him."