Militants aligned to ISIS have released a video claiming to show the execution of 11 Christians in restive north-east Nigeria.
The footage posted online late on Thursday by ISIS-linked propaganda arm Amaq showed 11 blindfolded men being shot and stabbed by militants from the Islamic State West African Province (ISWAP) at an undisclosed location.
"This is a message to Christians all over the world," said a masked man in the one-minute video.
He claimed the killings were in reprisal for the death of ISIS chief Abu Bakr al-Baghdadi and his spokesman.
ISIS leader Baghdadi committed suicide in October to avoid capture during a US special forces raid on his hideout in the province of Idlib in north-west Syria.
In recent months, ISWAP has intensified its attacks on Christians, security personnel and aid staff, setting up roadblocks on highways and conducting searches.
The United Nations on Tuesday condemned the "increasing practice by armed groups to set up checkpoints targeting civilians" in the north-east of Nigeria.
On Sunday, the militants killed six people and abducted five others including two aid workers when they intercepted vehicles on a highway on the outskirts of Maiduguri, the Borno state capital.
In a similar attack on December 5, ISWAP fighters disguised as Nigerian soldiers stopped and searched vehicles at a checkpoint near Maiduguri.
The group claimed in a statement that six soldiers and eight civilians, including two Red Cross workers, were among those abducted in that attack.
Last week the group released a video showing 11 alleged hostages.
One of the detainees in the video who identified himself as a school teacher said all the 11 hostages were Christians and appealed to the Nigerian government to secure their release.
ISWAP pledged allegiance to Baghdadi in 2016 and split from insurgent group Boko Haram.
It stepped up attacks on military outposts and troops in mid-2018, but has increasingly begun targeting civilians.
The decade-long militant insurgency in north-east Nigeria has killed 36,000 people and displaced around two million, according to the United Nations.
The violence had spread to neighbouring Niger, Chad and Cameroon, prompting a regional military coalition to fight the militants.