Islamic State has released a video which appears to show its militants killing 11 Christian men in Nigeria.The footage shows men in beige uniforms and black masks lining up behind blindfolded kneeling captives, before beheading 10 of them and shooting the 11th man.The militants said it was in revenge for the deaths of Islamic State leader Abu Bakr al Baghdadi and its spokesperson.The footage was posted on the terror group's online Telegram news channel on Thursday.

It featured captions in Arabic but no audio.In an earlier video seen by the Reuters news agency, the captives were said to have been taken from Maiduguri and Damaturu in the northeastern state of Borno, in which militants have tried to set up a separate Islamist state.The captives had pleaded for Nigeria's President Muhummadu Buhari and the Christian Association of Nigeria to intervene.The authenticity of both videos could not be verified.Militants split from Boko Haram in 2016 to form Islamic State in West Africa Province (Iswap), which has become the region's dominant jihadist group.Earlier this month, four aid workers taken from northeastern Nigeria were allegedly killed by the group.Islamist insurgents have killed about 30,000 people in the north of the country over the last decade.Islamic State's leader, al Baghdadi, was killed during a US operation in Syria in October.