A military source said five troops were killed at a base in Marte in Borno state.

"We lost five soldiers in the Marte encounter but I don't have any details on human losses in the other camps," said the source, who asked not to be named.

"We have to wait for the final assessment on the incidents to have a definite toll on casualties."

The Islamic State West Africa Province (ISWAP), the IS-linked faction of Boko Haram, said in an online statement its fighters attacked five bases in Borno at the weekend, destroying vehicles and carting away weapons, according to SITE Intelligence which monitors jihadist activities worldwide.

ISWAP claimed its assault on bases in the towns of Marte, Kirenowa and Dikwa killed 14 troops, but AFP could not independently verify the toll.

The group also claimed to have destroyed six trucks and an armoured vehicle, and said its fighters made off with two vehicles and an "array of weapons and ammunition as spoils".

On Monday, military and militia sources told AFP the extremists had overrun bases in Marte, Kirenowa and Dalwa, while an assault on Dikwa was repelled.

The jihadists were believed to have launched the attacks from their Lake Chad enclave where the military has intensified aerial attacks on ISWAP camps.

ISWAP has targeted dozens of military bases since July, killing scores of soldiers.

Also on Tuesday, Boko Haram factional leader Abubakar Shekau released a 35-minute video after months of silence, uttering jihadist doctrine from religious texts.

In his last appearance, in September, Shekau had claimed a string of attacks on military and civilian targets, which he did not do this time.

Boko Haram's decade-long campaign of violence has killed 27,000 people and displaced about two million in Nigeria.

The violence has spilled over into neighbouring Niger, Chad and Cameroon, prompting a regional military coalition to defeat the jihadist group.