ABUJA (Reuters) - Nigerian Islamist sect Boko Haram released a video purporting to show it beheading two men, its first online posting using advanced graphics and editing techniques similar to footage from Islamic State.
The film, released on Monday, shows militants standing behind the two men who are on their knees, hands tied behind their backs, with one man standing over them, holding a knife.
One of the kneeling men is made to tell the camera that they were 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 raise concerns that Boko Haram, which evolved out of a clerical movement focused on northeast Nigeria, is expanding its scope and seeking inspiration from international militant networks including al Qaeda and Islamic State.
Nigeria's President Goodluck Jonathan has said Boko Haram is allied to both al Qaeda and IS, though that has not been confirmed by Boko Haram itself.
The group previously had links to al Qaeda and though Boko Haram and IS have acknowledged each other, the Nigerian militants have not officially pledged allegiance to IS leader Abu Bakr al-Baghdadi.
"(Boko Haram) does refer to its fighters as soldiers of the Caliphate, and pro-IS jihadists worldwide now refer to it as the Caliphate's link in Nigeria," Laith Alkhouri, director of Middle East and North Africa research and jihadi threat intelligence at Flashpoint Partners, said.
Boko Haram has killed thousands and kidnapped hundreds in its bid to carve out an Islamist state in its homeland, and in recent months has increased cross-border raids into Cameroon, Chad and Niger.
The group came to control an area the size of Belgium but the Nigerian army, helped by Chadian troops, has recaptured some territory in the last few weeks.
Nigeria attracted international criticism for postponing its Feb. 14 presidential election by six weeks for security reasons linked to the insurgency, an excuse viewed as political interference.
The improved video quality comes soon after the group began to establish a social media presence this year through a communications unit, Al-Urwa Al-Wuthqa. Previously, Boko Haram would leak videos to selected journalists.
The media unit opened its first Twitter account in January. It was shut down and replaced on March 1 by a new one, where it has begun publishing videos and statements in English, French and Arabic.
It would be difficult to determine whether the Twitter accounts are authentic or represent only a faction. But the move mimics IS, which has waged a strong campaign on the platform and had many accounts shut down, Mark Singleton, director of the International Centre for Counter-Terrorism in The Hague, said.
"Not surprisingly they are trying to emulate IS where they can," Singleton said, "Beheadings have proven their media value ... apparently that's the way to get people's attention."
After taking over swathes on Iraq and Syria, Islamic State gained further notoriety by posting a video showing the beheading of American journalist James Foley in August followed by several more similar executions.
The Boko Haram film's use of graphics, the footage of black-clad militants with a black flag, and the editing to show only the aftermath of the beheading, were similar to material from Islamic State.
In the video, one of the victims says he comes from Baga in Borno state, and says the other is from Michika in Adamawa state, both areas where the army says it has recently recaptured territory from Boko Haram.
Past Boko Haram films have been much cruder affairs, often featuring a man identified as their leader Abubakar Shekau talking more about local complaints than global jihad. A number of recent releases have included much more gruesome footage of beheadings.
The latest video, entitled "Harvest of Spies", includes introductory animation with streaming computer code on a purple background before the start of the main event.
"(It) mimics the production of many IS videos ... the suspenseful slow motion scenes, the beheading of the individuals after confession of so called crimes, and the multilingual aspect including subtitles," Alkhouri of Flashpoint said.
Editing by Andrew Heavens and Giles Elgood