Following the beheading of British hostage David Haines by Islamic State (IS) extremist group, Prime Minister David Cameron Sunday said his country will hunt down the killers of the aid worker, a media report said.

“We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes,” BBC quoted Cameron, who presided over a British emergency committee Cobra over the issue, as saying.

Hailing Haines as a “British hero”, he said Britain will take “whatever steps are necessary” to keep the country safe.

Britain had to confront and “ultimately destroy” the “menace” of IS in a “calm, deliberate” way, he added.

The prime minister told BBC: “Step by step, we must drive back, dismantle and ultimately destroy IS and what it stands for.”

Haines, 44, was taken hostage in Syria’s Idlib province in March 2013. He was helping a French agency deliver humanitarian aid, having previously helped people in Libya and South Sudan.

The IS released a video Saturday of his beheading, a video similar to those of the recent executions of two US journalists, James Foley and Steven Sotloff, which were also posted online.

A masked IS militant said the execution of Haines was in retaliation for Cameron’s promise to join a US-led coalition to fight the IS.

The militant also threatened to kill another British hostage named Alan Henning, if Cameron continued to support the fight against the IS.