Al-Qaeda in the Arabian Peninsula (AQAP) has rejected Isis's claim to have established a caliphate in the heart of the Middle East, and condemned the group for spreading discord within the global jihadist movement.
The announcement seems to end the possibility that AQAP will imminently form a terrifying alliance with Isis (Islamic State), with the Yemen-based group having previously offered tentative support for militants and urged jihadists to unite.
In the video, released today, AQAP religious official Harith bin Ghazi al-Nadhari, also renews the group's pledge of loyalty to al-Qaeda leader Ayman al-Zawahiri.
Islamic State split from al-Qaeda ealier this year, after refusing to limit its operations to Iraq, and has fought the al-Qaeda backed Jabhat al-Nusra in the Syrian civil war.
AQAP is behind a number of plots targeting airliners in the West using concealed explosives, and is considered to be one of the world's deadliest terror groups, leading analysts to fear the outcome of an alliance between the groups.
The speech is a reaction to an announcement given by Isis leader Abu Bakr al-Baghdadi on 13 November, in which he welcomed pledges of loyalty by jihadist groups and announced the expansion of Islamic State to countries including Libya, Algeria, Saudi Arabia and Yemen, in an apparent snub to AQAP, who are are locked in combat with government forces there.
In the speech, al-Nadhari condemns al-Baghdadi for proclaiming the establishment of a Caliphate in June, in lands the group seized in Iraq and Syria, arguing that it had divided jihadists.
He argues that Muslim authorities had not approved the Caliphate, rendering it illegitimate.
"The announcement of the caliphate for all Muslims by our brothers in the Islamic State did not meet the required conditions," he states.
"The policy of our brothers in the Islamic State split the ranks of the mujahideen, and scattered them, in this sensitive phase in the history of the mujahid ummah [community] ," al-Nadhari announces.
"This is one of the absolutely forbidden matters in the religion of Allah."
He dismisses Islamic State's claims to authority outside Iraq and Syria, and accuses the group of taking "dangerous steps", condemning them for spilling Muslim blood.
"We make them bear responsibility" for "going too far in interpretations in terms of spilling inviolable [Muslim] blood under the excuse of expanding and spreading the power of the Islamic State," al-Nadhari says, according to a translation by the SITE monitoring service.
He renews the groups pledge of loyalty to al-Zawahiri, and says that the declaration is necessary as "campaigns of the enemy from among the apostates and Crusaders have intensified on all the fronts."