Islamic State West African Province on Thursday claimed its fighters killed eight Nigerian soldiers in an attack in Borno State.
The terror group said on ISIS propaganda arm Amaq that it also destroyed three army vehicles during the attack.
Nigerian army authorities are yet to react to the attack.
ISWAP claims came a day after a security source told AFP that three soldiers were killed in an intense fight between the troops and jihadists over a key northeastern garrison town.
“The soldiers died when an army vehicle burst into flames after a car filled with explosives rammed into a convoy on Tuesday afternoon,” the source told AFP.
On Saturday, Chad withdrew 1,200 troops from the region – including hundreds from Monguno – after completing a nine-month mission fighting a rival jihadist group – Boko Haram.
The pullout from the largest base in the volatile Lake Chad region, which straddles the borders of Nigeria, Niger, Cameroon and Chad, had sparked widespread fears of increased jihadist attacks.
On Tuesday, dozens of ISWAP fighters aboard several trucks fitted with machine guns attacked Monguno.
Residents in Monguno said a rocket-propelled grenade struck a refugee camp housing thousands of people, causing a fire that gutted hundreds of tents.
“We still don’t know if anyone was killed in the camp but some people sustained burns,” said Monguno resident Kulo Gana.
Residents also said jihadists ambushed buses carrying civilians under military escort outside the town, sparking a gun battle.
Soldiers who repelled the attack killed many of the jihadists, witnesses said.
Militants also stormed a compound housing the offices of aid agencies working in the region.
Contributions from AFP