LONDON — British officials are reviewing security measures Sunday after a hoax caller pretending to be the director of the government's eavesdropping agency managed to get through to Prime Minister David Cameron on the phone.

Cameron ended the call when it became clear the call, purportedly from GCHQ director Robert Hannigan, was a hoax, Downing Street said. No sensitive information was disclosed.

Officials said a separate hoax call was made earlier Sunday to GCHQ, resulting in the disclosure of a cellphone number for Hannigan.

"The mobile number provided is never used for calls involving classified information," officials said in a statement.

All government departments have been alerted for similar calls and security procedures are being reviewed.