Two blasts ripped through a mosque and market on Tuesday in the town of Mubi, Adamawa state, in an attack that bore all the hallmarks of Boko Haram jihadists.
The official death toll on Wednesday rose to at least 29 but local residents, a hospital source and rescue worker told AFP that many more died.
One worker at Mubi’s only cemetery said they were “shocked” to hear about the lower toll.
“We worked up to 9:00 pm burying bodies. By the time we closed, we had 76 graves. We buried 76 people yesterday (Tuesday),” he said, asking to remain anonymous.
“Today, as at 3:00 pm (Wednesday), 10 more bodies were brought in and buried. These people died overnight from injuries, obviously.”
Another gravedigger, who also asked for his name not to be used, supported the account. “We hope we are done with the burials,” he added.
Imam Garki, head of operations for Adamawa and Taraba states at the National Emergency Management Agency (NEMA), said two of the 11 people critically injured had died overnight.
“The total number of deaths is 30. The others are responding to treatment,” he said.
Ahmed Sajo, information commissioner for Adamawa state who gave the lower death toll of 29, said it was “possible people could have identified their relations and taken them home without going to the hospital”.
“In that case, we have no way of knowing how many of such cases there were. it’s possible some people could have buried their dead without taking them to hospital.”
Conflicting death tolls are not uncommon in Nigeria and the authorities have previously under-reported casualties in the Boko Haram conflict.
Tuesday’s attack came a day after US President Donald Trump promised his visiting Nigerian counterpart, Muhammadu Buhari, greater support in fighting the Islamist extremists.
Buhari and the military have long maintained the Islamic State group affiliate is a spent force and on the verge of defeat but repeated attacks and raid in the northeast suggest otherwise.