Residents the northeast Nigerian town of Damaturu say explosions and gunfire are being heard in the town, in the latest attack by suspected Islamic extremists.

Resident Garba Musa said Boko Haram attackers burned down a mobile police base early Monday in Damaturu, the capital of Yobe state. A helicopter gunship has arrived.

Fearful residents locked themselves into their homes but civil servant Abdullahi Abba said he fled into the bush with his family.

Boko Haram has increased the frequency and deadliness of its attacks and is holding a couple of dozen towns and villages along the border in the northeast where it has declared an Islamic caliphate.

The extremists are blamed for a Friday bomb attack that killed 102 people praying at the main mosque in northern Kano city.