Al Qaeda's North African wing has rejected the mediaeval-style caliphate declared by a militant Islamist group in Iraq and Syria, and confirmed its allegiance to al Qaeda leader Ayman al-Zawahri, a statement posted on social media said, according to Reuters.

The group calling itself the Islamic State announced last month it was creating a caliphate on lands it has captured in Syria's civil war and during a rapid advance through swathes of Iraq.

In a direct challenge to al Qaeda, its leader Abu Bakr al-Baghdadi assumed the title of caliph and issued a message seeking to assert authority over Muslims everywhere and rally them for jihad, or holy war. The Islamic State is an offshoot of al Qaeda, whose global leadership has disowned it.

The statement attributed to Al Qaeda in the Islamic Maghreb (AQIM) criticized Baghdadi's group for failing to consult with jihadi leaders, according to SITE, an authoritative U.S.-based organization that monitors Islamist militant communiques.

"We confirm that we still adhere to our pledge of allegiance to our sheikh and emir, Ayman al-Zawahri," the statement said, referring to the Egyptian who took on al Qaeda's leadership after U.S. special forces killed Osama bin Laden in 2011.

AQIM was originally based in Algeria, but has expanded more widely across the Sahel region of North Africa. Its leader Abdelmalek Droukdel has been loyal to the core al Qaeda leadership alongside other Islamist militant groups in the region.