Foley's ISIS captors demanded $143m ransom

The Islamic militant group ISIS once demanded a ransom of 100 million euros (A$143 million) from the family of James Foley, the US journalist who was beheaded this week.

GlobalPost, the news organisation Foley was freelancing for when he was captured in Syria in 2012, said the demand was made "during an initial period of communication with Jim's captors from November to December of 2013".

Philip Balboni, the chief executive of GlobalPost, told The Wall Street Journal that all communication was shared with government authorities but he declined to discuss how they replied to the ransom demand.

It has also been revealed that US special forces mounted an unsuccessful mission inside Syria last month to try to rescue Foley and other American hostages held by Islamic extremists.

US Barack Obama ordered the secret mission but it failed because the hostages were not where intelligence reports said they were.

A grisly video posted online by ISIS this week showed the moments before — and after — Foley, 40, was beheaded. He is seen kneeling on the ground in an orange tunic, hands bound behind his back, and reading from a prepared statement before a masked man dressed in black puts a knife to his throat.

The US has responded to the video by sending warplanes to launch air strikes on jihadist targets in Iraq.