Intense fighting between the military and Islamist militants in northern Nigeria is reported to have killed at least 185 people, however the army has disputed this figure.
Rocket-propelled grenades and heavy gunfire bombarded the remote town of Baga near the border with Chad for hours on Friday evening, officials say.
Some 40% of the town was destroyed by fire, one rescue worker said.
Nigeria faces a long-running insurgency in its predominantly Muslim north.
The Boko Haram insurgency has left thousands of people dead since 2009.
Residents of Baga fled into the bush and only returned on Sunday afternoon to find much of the town destroyed and human and animal corpses strewn through the streets.
One local journalist said this marked a significant escalation in the insurgency in the area, with the militants using heavier weapons than in previous attacks.
BBC Nigeria correspondent Will Ross says this may prove to be the most deadly incident involving Boko Haram since a series of bombings in January last year in Kano left at least 160 people dead.
One resident, Bashir Isa, told Associated Press: "Everyone has been in the bush since Friday night; we started returning to town because the governor came.
"To get food to eat in the town now is a problem because even the markets are burnt. We are still picking corpses of women and children in the bush and creeks.''
Residents said most of the bodies had been burned beyond recognition in blazes that had destroyed much of the town.
"Forty percent of the town has been gutted by fire. Many residents are still unaccounted for and for now it is assumed that they fled into the bush," one rescue official, who did not want to be named, told the AFP news agency.
Bodies are still being found and buried on Monday, two of the town's inhabitants told BBC Hausa.
One eyewitness told the BBC that the fighting started when gunmen entered a video-viewing centre, looking for a man, who then fled.
The militants opened fire, attracting the attention of nearby soldiers, who were initially overpowered, before returning with reinforcements, leading to a fierce gunbattle, he said.
Local official Lawan Kole said that 185 people - including civilians, members of the security forces and attackers - had been buried.
However, Borno state military spokesman Lt Col Sagir Musa told AFP that such a high number of deaths was "unthinkable".
"On my honour as an officer, nothing like that happened."
Correspondents note that the Nigerian military often plays down the number of people killed in clashes with militants.
An unnamed local official told AFP that dozens of people had been killed in the fighting.
Communications with parts of northern Nigeria are difficult since mobile phone masts were destroyed by militants.
Isa Umar Gusau, an adviser to Borno state's governor, told BBC Hausa:
"It is very difficult to establish the number of casualties exactly.
"The figure of casualties given might not be correct, but we value human life. We regret the loss of even one live of any human being in Borno state."
Boko Haram wants to carve out an Islamic state in northern Nigeria.
Its name in the local Hausa language means: "Western education is forbidden".