A former hostage held by Islamic State militants has revealed US journalist James Foley, who was beheaded in a video released on Tuesday, had previously tried to escape from his captors.

Nicolas Henin, a freelance French reporter who was captured in 2013 and remained a prisoner for 10 months before his release in April, said Foley had received a "brutal punishment" for planning to escape.

Speaking to ABC News, Henin said Foley had been punished both for his escape plans and as an outlet for the militants' frustrations over the US "war on terror".

"James was a bit punished for a presumed attempt to escape, but it had no real chance," he said.

Henin, who had been held alongside Foley for around seven months, said he was not willing to provide details of the nature of the punishments out of respect for Foley's family. He added that the video was "extremely shocking" because he could easily have been in Foley's place.

"For instance, the shoes that he was wearing when he was taken to this place in the desert, I wore them. We had few shoes that we were using to go to the bathroom and we were sharing them," he said.

Foley was executed by a militant from the Islamic State, allegedly with a British accent, at an undisclosed location in a video released this week. The 40-year-old journalist was taken hostage while reporting in Syria in November 2012.

The news of his attempted escape comes as the Pentagon announced that in the months leading up to Foley's death, the US launched a risky but unsuccessful rescue mission in Syria.

Confirmation of the failed night-time raid, which took place earlier this summer, came after a day of debate over whether the Obama administration had done enough to save Foley's life.

It represented the first confirmation of US military operations in insurgency war-ravaged Syria, where Isis gestated into the jihadist organisation that has redrawn the borders of the Middle East.

On Wednesday, President Barack Obama pledged to "confront this hateful terrorism and replace it with a sense of hope and civility".

IS militants reportedly demanded a multi-million dollar ransom in exchange for Foley's release, but the US reportedly refused to pay it before he was killed.

According to the New York Times, the group pressed the US to provide $100m, according to a representative of Foley's family and a former hostage held alongside him.