It's reported an American journalist who was beheaded by Islamic State militants was among a group of hostages the US military tried to free this summer.

The Pentagon has revealed a secret mission took place recently to rescue American citizens held in Syria - but they were not located.

Last night US President Barack Obama described the killing of James Foley as "an act of violence that shocks the conscience of the entire world";

Meanwhile, gardai are said to be monitoring 30 jihadi fighters as part of international efforts to stop terrorism.

The Irish Independent sites garda sources as saying the group is using Ireland as a base while travelling to conflict zones in Syria and Iraq.

The details emerged in the wake of the murder of US journalist James Foley, who was executed by Islamic State militants, one of whom appeared to have a British accent.

A video seen by the Independent contains footage of a man claiming to be half Irish and half Nigerian - and fighting for the Islamic State.