US military tried but failed to free Foley

A US secret military mission had tried but failed to free US reporter James Foley and other American hostages in Syria, the BBC reported, citing US officials.

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."

In a statement on Wednesday, the Pentagon said that the US "attempted a rescue operation recently to free a number of American hostages held in Syria."

It said the operation "involved air and ground components and was focused on a particular captor network within ISIL" (the former name of IS).

"Unfortunately, the mission was not successful because the hostages were not present at the targeted location."

The statement did not specify whether the operation had intended to rescue Foley, who was kidnapped in Syria in November 2012.