Nigeria's Islamist sect Boko Haram released a video purporting to show it beheading two men, its first online posting using advanced graphics and editing techniques reminiscent of footage from Islamic State.
The film, released on Monday, shows militants standing behind the two men who are on their knees, their hands tied behind their backs, with one man standing over them, holding a knife.
One of the men is made to tell the camera that they had been paid by authorities to spy on the militant group, before the film moves to another scene showing their decapitated bodies. It was not possible to confirm the film's authenticity or date.
The footage will stoke concerns that Boko Haram, which evolved out of a clerical movement focused on northeast Nigeria, is expanding its scope and seeking inspiration from global militant networks including al Qaeda and Islamic State.
The militants who have killed thousands and kidnapped hundreds in their bid to carve out an Islamist state in their homeland, have in recent months stepped up cross-border raids into Cameroon, Chad and Niger.