Gunfire and explosions rang out through Nigeria's main northern city of Kano on Tuesday, as Nigerian forces battled Islamist militants in a raid on one of their hideouts, witnesses and the military said.
Residents of the Sabuwar Gandu area of Kano awoke to several loud blasts and a raging gun battle. There were no immediate reports of casualty figures.
"Our men just raided one of the hideouts of the elements ... where we discovered explosives and weapons," said a spokesman for the Joint Task Force in Kano, Lieutenant Iweha Ikedichi.
After a relative lull, Boko Haram attacks have surged in the past few days, dampening hopes that tighter security in the north had drastically reduced their capability.
The shadowy sect says it is fighting to reinstate an ancient Islamic caliphate in Africa's most populous nation, whose 160 million people are split roughly evenly between Muslims and Christians along north-south lines.