Riding in trucks fitted with anti-aircraft guns, fighters from the self-styled Islamic State West Africa Province (ISWAP) faction of Boko Haram launched a raid late Tuesday on troops in the town of Gudumbali, sparking a fierce firefight in which two soldiers were injured, a military officer said.

"It was a tough battle," said the military officer who asked not to be named as he was not authorised to speak to the media.

"Troops fought hard and repelled the terrorists, two soldiers were injured in the fight," he said, adding the base was on "high alert" for a follow-up attack.

On Monday, ISWAP fighters had attacked another base in the town of Malam Fatori near the border with Niger, which was repelled with air support, according to two military sources who said a soldier was killed and several injured in the attack.

An ISWAP attack Saturday on soldiers in Buni Gari village, in Yobe state, left eight soldiers dead, the Nigerian army confirmed on Tuesday.

Sources said air support and reinforcements from a military base in the nearby town of Buni Yadi helped push the militants out.

The ISWAP faction has in recent months intensified attacks on military targets in Borno and neighbouring Yobe state, prompting questions about the military's grip on security.

When the Malam Fatori army base was attacked, it was already sheltering a contingent of soldiers who had abandoned another base near the fishing town of Baga on the shores of Lake Chad.

The soldiers had run out of ammunition during a fierce gun battle on November 30, in which one was killed and seven injured.

- 1.8 million homeless -

"They didn't received supplies and decided to leave the base and move to Malam Fatori on Saturday," the first military officer said.

"They had no ammunition to fight in case of renewed attack and had to abandon the base," said the second military officer.

Since July, AFP has reported at least 22 attacks on military bases and positions in Borno and Yobe.

ISWAP claimed responsibility for most of them.

The Nigerian military has hit out at media reporting of the attacks and even threatened legal action against organisations for publishing unofficial casualty figures.

Borno and Yobe, along with nearby Adamawa state, have borne the brunt of nine years of jihadist violence that has claimed 27,000 lives and devastated the remote region.

Some 1.8 million people are still homeless while aid agencies are grappling with a humanitarian crisis triggered by the conflict.