CAIRO — An Internet video released Friday purports to show an Islamic State group fighter beheading British hostage Alan Henning and threatening yet another American captive, the fourth such killing carried out by the extremist group now targeted in U.S.-led airstrikes.

The video mirrored other beheading videos shot by the Islamic State group, which now holds territory along the border of Syria and Iraq. It ended with an Islamic State fighter threatening a man they identified as an American.

“Obama, you have started your aerial bombardment of Shams (Syria), which keeps on striking our people, so it is only right that we continue to strike the neck of your people,” the masked militant said.

The Associated Press could not immediately verify the video’s authenticity, though it was released in the same manner as other Islamic State group videos and the masked militant sounded similar to the one who carried out the other slayings.

The British Foreign Office had no immediate comment, nor did officials in Washington.

Henning, 47, nicknamed “Gadget,” had joined an aid convoy and was taken captive on Dec. 26, shortly after crossing the border between Turkey and Syria. Earlier this week, Henning’s wife Barbara Henning asked the militants in a televised plea: “Please release him. We need him back home.”