A Nigerian militant group on Saturday announced the deaths of seven workers from a construction company who had been taken hostage last month.

The group, Ansar al-Muslimeen (widely known as Ansaru), released video stills of some of the bodies and blamed the deaths on a joint Nigerian-British military operation intended to free the hostages. There was no immediate word from those governments.

The militants on February 18 claimed responsibility for the kidnappings of the seven construction workers taken from their office in northeastern Nigeria.