Jihadist fighters have killed 13 soldiers in northeastern Nigeria, two army sources told AFP on Monday.
Heavy gunfire and rocket-propelled grenades hit a military convoy in Gazagana village, in Yobe state on Saturday.
"We lost 13 soldiers in this ambush and several were injured," an officer said.
But The Nigerian army, which tends to give far lower official figures for losses, said on Sunday that 28 jihadists had been "neutralised and only one soldier had died.
The convoy was headed for a military base at Buni Yadi, another 20 kilometres from Damaturu, said the second army source, who gave the same death toll.
"It was a fierce battle and the terrorists also suffered casualties," he said, without giving a figure.
The attack was blamed on the Islamic State West Africa Province group, an affiliate of the Islamic State Group.
ISWAP was linked to Boko Haram until it split from the group in 2016
Since 2009, the jihadist campaign in northeast Nigeria has focused on Borno where the Boko Haram group is also active.
At least 36,000 have been killed in the 11-year conflict and about two million have been displaced from their homes.
The violence has also spread into neighbouring Niger, Chad and Cameroon.
A regional military coalition is in action to fight the militants.