The incidents are the latest against military targets in the restive region over several months that have raised concerns about a resurgence of the Islamist militants.

Insecurity is an election issue as President Muhammadu Buhari, who is seeking a second term at polls next month, came to power in 2015 on a pledge to defeat the jihadists.

More than 27,000 people have been killed since the insurgency began in 2009.

On Friday, troops repelled a dawn attack by fighters loyal to Boko Haram factional leader Abubakar Shekau in Banki on the border with Cameroon, a military officer told AFP.

"The attack was successfully repelled and the terrorists were pushed back," said the officer, who asked to remain anonymous as he was not authorised to speak to the media.

There were no reports of casualties.

Banki is 130 kilometres (80 miles) southeast of Maiduguri, the Borno state capital, and houses some 45,000 people displaced by the conflict in a sprawling camp.

There have been several previous attacks on troops and the displaced in Banki, underlining the precarious situation for tens of thousands of people made homeless by the fighting.

On Wednesday, fighters from IS-affiliated Islamic State West Africa Province (ISWAP), overran two military bases in Borno and neighbouring Yobe state.

The first happened at about 5:50 pm (1650 GMT) in Gaidam, in Yobe state, and also saw shops looted and burned down.

One local man said some of the insurgents were known to residents.

Residents reported seeing a charred body near two burnt tanks but it was not clear if the body was that of a soldier or a jihadist.

A civilian militia member in Gaidam gave a similar account and said the insurgents were seen at a petrol station, filling up their vehicles.

The ISWAP convoy of more than 20 vehicles was seen on Thursday heading towards the town of Damasak, on the border with Niger, he added.

The second attack happened about an hour later in Ajiri village in the Mafa area of Borno, according to a military source and a civilian militia leader in Maiduguri.

Three soldiers were reportedly killed but again, there was no official confirmation from the army.