London, March 8 (IANS): In an audio message posted online, the Boko Haram militant group has pledged allegiance to the Islamic State (IS) radical Islamist group, a media report said on Sunday.

"We announce our allegiance to the caliph of the Muslims ... and will hear and obey in times of difficulty and prosperity, in hardship and ease, and to endure being discriminated against, and not to dispute about rule with those in power, except in case of evident infidelity regarding that which there is a proof from Allah," said Boko Haram leader Abubakar Shekau in the message posted on Twitter on Saturday.

The message identified the caliph as Ibrahim ibn Awad ibn Ibrahim al-Awad al-Qurashi, who is better known as Abu Bakr al-Baghdadi, the leader of IS and self-proclaimed caliph of the Muslim world, The Guardian reported.

Baghdadi has already accepted pledges of allegiance from other jihadi groups in the Middle East, Afghanistan, Pakistan and north Africa.

The Islamist militant group Boko Haram, whose name in the local dialect translates into "Western education is sin", seeks to impose the Islamic Sharia law in the constitution of Nigeria, Africa's most populous country.