UPDATE 1-Blasts heard as Nigerian army battles Islamists in Kano

(Updates with details, military spokesman)

By Bala Adamu

KANO, Nigeria Feb 22 (Reuters) - Gunshots and explosions rang out on Wednesday in Nigeria's biggest northern city Kano, as the military exchanged fire with suspected militants from the Boko Haram Islamist sect.

Clashes between Boko Haram gunmen and security forces have flared up several times in Kano since the sect killed 186 people in Nigeria's second largest city last month, its deadliest attack so far.

"There was a shootout and four arrests were made while the early morning operation lasted," local spokesman for the Joint Military Taskforce (JTF) Ikedi Iweha Ikidichi said, declining to take further questions.