A US secret military mission had tried but failed to free US reporter James Foley and other American hostages in Syria, US officials have said.

Their comments come after a video of Foley's beheading by Islamic State (IS) militants appeared on Tuesday.

IS said Foley's death was revenge for US air strikes on its fighters in Iraq.

US President Barack Obama condemned the killing as "an act of violence that shocks the conscience of the entire world".

He compared IS militants, who control large parts of Syria and Iraq to a "cancer" and said the group's ideology was "bankrupt".

The UN, UK and others have also expressed abhorrence at the video.

Mr Foley's mother Diane said he "gave his life trying to expose the world to the suffering of the Syrian people".

The Committee to Protect Journalists said it was "extremely concerned for all journalists" still held by IS, describing Syria as "the world's most dangerous place to be a reporter".

(BBC)