IS `Accepts` Boko Haram's Oath of Allegiance

Islamic State (IS) has reportedly accepted a pledge of allegiance from the Nigerian insurgent movement Boko Haram.

The acceptance of the allegiance was made in an audio recording, which was posted on IS-related websites on Thursday, Al Jazeera reports.

The voice in the audio message, which is attributed as belonging to IS spokesman Mohammed al-Adnani, calls for expansion of the caliphate to West Africa.

The voice assures that IS leader Abu Bakr al-Baghdadi, who the insurgents style as their caliph, has accepted Boko Haram's oath of allegiance.

A voice, attributed to Boko Haram's leader Abubakar Shekau, pledged an allegiance to IS on Saturday in an audio recording, which was posted on the armed group's Twitter page.

Boko Haram has been fighting against the Nigerian government since 2009 in an attempt to establish an Islamic state in the north of the country, which is predominantly Muslim.

Meanwhile, in the latest audio IS issued new threats to the West, threatening to target iconic buildings such as the White House, Big Ben and the Eiffel Tower.