The monitoring group could not immediately verify the statement distributed on Twitter purportedly from supporters of Al Qaida in the Arabian Peninsula (AQAP) based in central Yemen.

AQAP is considered the most powerful branch of the global militant network headed by Ayman Al Zawahiri and has previously rejected the authority of Daesh, which has declared a caliphate in swathes of Iraq and Syria.

State authority in Yemen has unravelled since the Al Houthi militia formally seized power last week and the AQAP has sworn to destroy it, stoking fears of sectarian civil war.

“We announce the formation of armed brigades specialised in pounding the apostates in Sana’a and Dhamar,” the purported former AQAP supporters wrote, referring to two central provinces.

“We announce breaking the pledge of allegiance to the shaikh, the holy warrior and scholar Shaikh Ayman Al Zawahiri ... We pledge to the caliph of the believers Ebrahim Bin Awad Al Baghdadi to listen and obey,” they said, referring to the radical group’s leader who is also known as Abu Bakr Al Baghdadi.

Militants in Egypt’s Sinai Peninsula and Libya have also joined Daesh, signalling a competition for loyalty among armed Islamists battling states in the Mideast and North Africa.