Militants from Islamic State (ISIS) claimed to have killed James Foley, an American journalist who was kidnapped in Syria nearly two years ago. The extremist group also threatens the life of another American if President Barack Obama doesn't end military operations in Iraq.

James Foley [Photo/sina.com.cn]

A video released on Tuesday showed a masked ISIS fighter beheading a kneeling man dressed in an orange jumpsuit who is purported to be James Wright Foley, a photojournalist who went missing in Syria in 2012.

The masked executioner spoke in English, with what sounded like a British accent, and said that the slaying came in response to the airstrikes ordered by President Barack Obama against ISIS 12 days ago.

ISIS, whose chief spokesman came under State Department sanctions on Monday, warned of further revenge -- including on another man purported to be a captured U.S. journalist, Steven Sotloff -- and in the video, the victim was made to read a statement blaming the United States for his own murder.

Foley has been missing in Syria since November 2012, where he went to report on the bloody struggle to overthrow dictator Bashar al-Assad. He was reportedly forced into a vehicle by gunmen, and he was not heard again. At the time of his disappearance, he was working for the GlobalPost.