A TERROR group in East Africa has pledged allegiance to Islamic State’s commander in chief in a terrifying harbinger of the rise of the extremist group in the region.

A TERROR group in East Africa has pledged allegiance to Islamic State's commander in chief in a terrifying harbinger of the rise of the extremist group in the region.

The new organisation, calling itself Jahba East Africa, told its recruits to "leave al-Shabaab and their sponsor groups" and back ISIS chief Abu Bakr al-Baghdadi.

A statement published online declared "bayah" — an oath of allegiance — to Baghdadi, hailing him as the "rightful Khalifa [leader] of all Muslims".

The group criticises rival Islamist cell al-Shabaab, which has refused to join ISIS, revealing a split among the jihadi groups that have infected East Africa.

The statement reads: "Al-Shabaab has forgotten the resolved needed to work for the establishment of the rule of Allah.

"Al-Shabaab has now become a psychological and physical prison.

"The pledge bayah to caliph Abu Bakr al-Baghdadi is freedom for the mujahideen in East Africa and opportunity to wage jihad according to the Sunnah [traditions of the Prophet Mohammed] against the enemies of Allah."

Al-Shabaab has wreaked havoc across Somalia and East Africa in recent years, launching frequent attacks in its bid to overthrow the Western-backed government.

The group, whose name means "The Youth," seeks to impose its strict version of sharia law in Somalia, where it frequently unleashes attacks targeting security and government targets, as well as hotels and restaurants in the capital.

Al-Shabaab has also been behind deadly attacks in Kenya and Uganda, which both contribute troops to an African Union peacekeeping force in Somalia.

ISIS released a video in 2015 urging al-Shabaab members to join the death cult — also known by its Arabic acronym Daesh.

But only a handful of fighters from the predominantly Somali terror group have ever pledged formal allegiance to ISIS.