The United States and Nigeria conducted fresh strikes on Sunday against so-called Islamic State jihadists in northeast Nigeria's Borno State, the US military said Monday.

At least 20 jihadists were killed in the weekend strikes, according to the Nigerian military.

The strikes came shortly after another joint operation between the two militaries that killed Abu Bakr al-Mainuki, the deputy leader of the group's local West African "province."

Nigeria's military described Mainuki as the world's "most active terrorist."

His assassination marked the first successful targeting of a senior militant leader by Nigeria's security forces after more than a decade of insurgency by a number of armed groups in the north, including Boko Haram.What do we know about the weekend strikes on jihadists?