Isis has released a video that shows its militant fighters executing 11 Christians in Nigeria.

The militant group’s west African offshoot posted footage to Telegram on Boxing Day, showing men in uniforms and black masks beheading 10 blindfolded captives and shooting an eleventh prisoner.

The so-called Islamic State West Africa Province (Iswap), a faction of Boko Haram, gave no details of the captives’ identities, but an earlier video said they had been taken from the northeastern states of Borno and Yobe, where militants have been fighting for years to establish an Islamist state.

“We killed them as revenge for the killing of our leaders, including Abu Bakr al-Baghdadi and [Isis spokesman] Abul-Hasan al-Muhajir,” a member of the group’s media unit said, according to the journalist first sent the footage, Ahmad Salkida.

While some analysts suggested the killings had been timed to coincide with Christmas, Mr Salkida said the timing was more likely due to recent clashes in the area, following a spate of jihadist-driven skirmishes near the towns of Maiduguri and Damaturu.

“It’s obvious both violent groups [Iswap and Boko Haram] want to use the symbolism of Christmas day to drive their messages,” Mr Salkida​ wrote on Twitter.

“This is a coincidence because the two factions clashed earlier in the week with scores of casualties.”

The earlier video showed the all-male captives appealing for the Christian Association of Nigeria and President Muhammadu Buhari to intervene and save them, according to Reuters.

The footage was possibly an attempt to divide the country’s Muslim and Christian populations and pile pressure on the government to respond to militants’ demands, security analyst Kabiru Adamu told the BBC.

President Buhari said in a statement on Friday he was “profoundly saddened and shocked by the death of innocent hostages in the hands of remorseless, godless, callous gangs of mass murderers that have given Islam a bad name through their atrocities”.

“We should, under no circumstance, let the terrorists divide us by turning Christians against Muslims because these barbaric killers don’t represent Islam and millions of other law-abiding Muslims around the world,” he continued.

While the footage was released via Isis’ Amaq media agency, experts suggest that Iswap’s connection with Isis is more or less nominal, with the group likely receiving little in the way of funding or support from their allies in the Middle East.

But Islamist violence in Nigeria has increased in the past six months, the UN warned, with the agency’s acting humanitarian coordinator, Antonio Jose Canhandula​, condemning militants’ increasing practice of setting up fake checkpoints and abducting civilians.

Iswap is believed to be holding dozens of hostages – mainly soldiers, aid workers and those publicly aligned to the government.

The recent footage came as Mr Canhandula and UN secretary general Antonio Guterres condemned the alleged execution of dozens of civilians along the road linking Borno and Yobe on 23 December.

That same day, the Nigerian army killed 30 Iswap militants as they attempted to invade Damaturu, including the leading commander, local media reported.

On 24 December, a Nigerian soldier was killed defending the former president Goodluck Jonathan’s country residence in Bayelsa State from an attack by gunmen.

Calling on the government to do more to combat the rise in violence and protect civilians, Mr Canhandula said that in 2019 alone more than160,000 people fled their homes for shelter in already congested refugee camps.