David Cameron has stressed the UK's resolve to defeating the extremist group, Islamic State, telling the Commons that the UK "will never give in to terrorism".

At prime minister's questions on 3 September 2014, Mr Cameron condemned the "sickening and brutal" killing of American journalist Steven Sotloff by Islamic State militants.

He said there was "shock and anger" that the beheading appears to have been carried out by a British citizen. Another US journalist, James Foley, was similarly murdered last month.

Addressing MPs, the PM said: "It is important that we are clear about the nature of the threat we are facing...

"The only way to defeat it is to stand firm and send a very straight forward message - a country like ours will not be cowed by these barbaric killers."

Echoing Mr Cameron's sentiments, Labour Ed Miliband expressed his "universal sense of revulsion" at Mr Sotloff's killing, and his "deep concern" about threats to kill a British hostage who was shown in the latest video.

Mr Miliband noted "a pattern of murderous behaviour by ISIS of innocents" and asked the prime minister what the UK is doing - including through its chairmanship of the UN Security Council - to mobilise other countries and regional bodies against the organisation.

Mr Cameron said he was right to highlight that the fight against IS should not be seen as a "Western-led intervention".

He told MPs that the UK's aim is to marshal international support and backing for view that IS "is unacceptable and needs to be defeated".

The exchanges came after a meeting of the government's emergency Cobra committee following threats to kill the British hostage.

IS said the Briton, who has family in Scotland, would be killed unless US air strikes were halted.

Foreign Secretary Philip Hammond has said the government will look at "every possible option" to protect the hostage.