Obama says 'no just God' stands with ISIS in journalist's killing

US president Barack Obama has vowed to "do everything we can to protect our people" after terror group Islamic State (ISIS) posted a video of US journalist James Foley being beheaded.

Mr Obama, speaking from Massachusetts where he is holidaying, said he had spoken to Foley's parents and told them that "we are all heartbroken at their loss," NBC News reports.

"ISIL speaks for no religion," he said.

"Their victims are overwhelmingly Muslim and no faith teaches people to massacre innocents."

American warplanes struck ISIS targets 11 times overnight after the video was released.

ISIS has threatened the life of a second unless the US ends the airstrikes.