LAGOS, Nigeria (AP) — Islamic extremists continue to move freely between Nigeria and northern Mali, despite the ongoing French military operation there against them, the United States ambassador to Nigeria said Thursday.

As extremist shootings, bombings and kidnappings of foreigners continue unstopped across northern Nigeria, U.S. Ambassador Terence McCulley said halting the violence remained a top priority of the Washington government. However, McCulley declined to answer questions about U.S. plans to operate a drone base in neighboring Niger — which would allow the aircraft to monitor Nigeria as well.