Nigerian militant group Boko Haram's leader Abubakar shekau has posted a statement on the group's Twitter account, pledging allegiance to Islamic State (IS).
According to BBC, the message on the militant organization's Twitter account has not been verified as yet.
In the audio message posted by the Boko Haram leader, he announced "allegiance to the caliph".
In the past, the group was thought to have links with al Qaeda.
Boko Haram began a military campaign in Nigeria in 2009 to impose Islamic rule in the northern part of the country.
The conflict has since spread to the neighbouring states.
