The convoy was hit by militants from the Islamic State West Africa Province (ISWAP) outside the northeastern village of Metele on June 2, leading to a battle where one jihadi was able to detonate a suicide vehicle amid the troops, the sources said.
"We lost several men in the fierce battle with ISWAP terrorists from a vehicle-borne suicide attack," one of the sources told AFP.
"I can't give a definite toll but the loss is substantial," he said.
ISWAP on June 4 claimed responsibility for the ambush, which it said killed or wounded around 20 Nigerian soldiers, according to the SITE Intelligence group that monitors jihadi activities worldwide.
The military convoy was heading to the town of Arege, near the borders with Niger and Chad, to deliver food supplies to troops fighting the jihadis in the area, said the sources, who asked not to be named since they were not authorized to speak on the incident.
The convoy was near the fishing town of Baga when it "fell into an ambush" by ISWAP jihadis at around 1400 GMT on June 2, another security source said.
"The soldiers... were getting the upper hand when a suicide bomber set off his explosives-primed vehicles among the soldiers, and killed many of them," the source said.
ISWAP said the explosion also destroyed "two armored vehicles" and disabled four other vehicles," according to SITE.
The group also claimed to have seized weapons and ammunition during the attack.
The ISWAP jihadis, who split from the Boko Haram Islamist group in 2016, have since become the dominant insurgency group, focusing mostly on targeting troops and abductions.
In November 2018, ISWAP militants raided a base in Metele near the border with Niger in an attack that left at least 44 soldiers dead, though troops who survived put the death toll at more than 100.
The jihadi violence over the past 14 years has killed around 40,000 people and displaced more than two million in northeast Nigeria.
The conflict has also spilled into neighboring Niger, Chad and Cameroon, prompting a regional coalition to fight the militants.