Cameron made the remarks on Saturday after receiving a security briefing from the Foreign Office, intelligence and military officials, following the release of a video purportedly showing an ISIL militant beheading Alan Henning.

The UK prime minister added that the slaying demonstrated that the terrorists were committed to inflicting horror for horror’s sake, describing the murder of Henning as abhorrent, senseless and unforgivable.

Furthermore, Cameron said that the militants must be hunted down to be stopped. However, he declined to say whether Britain would extend its involvement in the US-led airstrikes on the ISIL positions in Syria, where the hostage killings are believed to have taken place.

Henning was the fourth Western hostage to be executed by ISIL militants since mid-August, following two US journalists James Foley and Steven Sotloff and British aid worker David Haines.

A masked ISIL member appeared in the video of Henning’s beheading, saying the execution was in response to Britain’s engagement in the US-led coalition against ISIL.

Henning, a taxi driver from the town of Eccles in northwest England, was a member of a group of volunteers that traveled to Syria in December 2013 to distribute food and water to people affected by the conflict in the country. According to his coworkers, he was abducted the day after Christmas by masked gunmen.

The Takfiri terrorists currently control parts of eastern and northern Syria and Iraq’s northern and western regions. They have threatened all communities, including Shias, Sunnis, Kurds, Christians, Izadi Kurds and others in Iraq, as they continue their atrocities