An Islamic State jihadist in Syria hacked into the email account of British government ministers, GCHQ sources told the Telegraph. An investigation by the intelligence agency found that hackers for the jihadist group targeted senior government ministers, including Home Secretary Theresa May in a sophisticated espionage operation.

Last week, Prime Minister David Cameron announced the death of three British Isis militants in drone strikes. The dead include hacker Junaid Hussein from Birmingham, who was jailed before he went to Syria, for hacking into the electronic diary of former Prime Minister Tony Blair.

By hacking the emails of ministers the jihadist would have been able to discover the public events members of the Royal Family and political figures were expected to attend. Among those killed in the drone strikes was Reyaad Khan from Cardiff, who was allegedly involved in a plot to assassinate the Queen.

Hussain, who joined Isis in 2013 with his British wife Sally Jones, is believed to be the mastermind behind the jihadist group's Cyber Caliphate hacking operation, which briefly gained control of a Pentagon Twitter account in January. He was killed in a US drone strike, while Khan and Rahul Amin, of Aberdeen, were the first British citizens to be killed in UK drone strikes.

It is not believed that any security breaches occurred, but officials were told to tighten security procedures and change passwords.

In August, the email addresses and passwords of US and UK government and military personnel was released by a pro-Isis account on Twitter.