US President Barack Obama and British Prime Minister David Cameron have said that the US and UK wont be "cowed by barbaric killers".
This comes following the release of video footage by Islamic State militants showing the murder of a second American journalist, and threats that a British hostage could be next.
The two leaders released a joint statement ahead of this week's NATO summit in Wales, calling for unity in targetting IS militants.
Prime Minister David Cameron said the threat of IS will dominate the talks.
IN: this so called Islamic State
OUT: plots and attacks already
DUR: 00:19
CLIP: http://www.fsnradionews.com/feeds/0904militants-cameron1.mp3
ALT: But according to former NATO arms controller Ted Say, the summit will probably result in a lot of talk and little action.
IN: They'll be wanting to
OUT: around the North Atlantic council table
DUR: 00:18
CLIP: http://www.fsnradionews.com/feeds/0904militants-say1.mp3