Nigeria, Jan. 9 -- Scores of fighters have been killed following a week-long violent clash between rival terrorist groups, Boko Haram and the Islamic State West Africa Province (ISWAP), across the Sambisa Forest and Mandara Mountains in Borno State.

The renewed hostilities reportedly began on January 3, when ISWAP launched a coordinated attack on Boko Haram camps around the Ali Ngulde axis of the Mandara Mountains.

The raid was said to be led by two senior ISWAP commanders, identified as Jundullah and Ibn Hataf.

Sources disclosed that Boko Haram fighters, under the command of a field leader known as Abu-Rijal (Ba-Sulhu), mounted a fierce counter-ambush, resulting in the deaths of dozens of ISWAP fighters. Several others were reportedly...