Gun battles broke out in the remote fishing village of Baga on Friday, forcing residents to flee the town that also serves as a small trading center on the shores of Lake Chad. People only started to return to their homes on Sunday.
News about the extent of the fighting began to emerge on Monday, with local government officials and the Red Cross estimating at least 187 killed.
"So far 187 have been buried, while 77 are under admission in hospitals," Red Cross spokesman Nwakpa O. Nwakpa told the AFP news agency. He added that 300 houses had been burned to the ground.
A spokesman for UN Secretary-General Ban Ki-moon said that the secretary general was "shocked and saddened at reports of high numbers of civilians killed," adding that he urged "all concerned to fully respect human rights and safeguard the lives of civilians."
Casualty figures disputed
The Nigerian military has dismissed the death toll as exaggerated.
"There could have been some casualties, but it is unthinkable to say that 185 people died," Borno state military spokesman Lieutenant Colonel Sagir Musa told the news agency AFP, calling media reports "extensively inflated."
Defense spokesman Brigadier General Chris Olukolade told the Reuters news agency that 25 militants and one government soldier were killed.
Nigeria's security forces have frequently minimized casualty figures in the conflict with Boko Haram. Resentment of the military runs high in some communities, however, and locals have been known to inflate death tolls and accuse the military of indiscriminately killing civilians.
Borno state spokesman, Umar Gusau, said that the number of dead was difficult to determine, as many of the victims had already been buried.
The village of Baga lies in Borno state, home base of the Boko Haram Islamists blamed for carrying out scores of attacks across northern and central Nigeria since 2009.
"For now, we don't have a very good basis for the figure," Gusau told Reuters. "These people say… they have buried them. From my experience, most times residents exaggerate figures."
Unclear how battle began
Residents told a delegation led by regional Governor Kashim Shettima that clashes started when troops surrounded a mosque allegedly sheltering insurgents.
But one resident told AFP that the battle began when the gunmen tried to burst into a viewing center, where locals watch football matches. The gunmen opened fire when one local began to run, prompting government troops to intervene.
Including people killed by security services, the conflict between Boko Haram and the Nigerian government has left an estimated 3,000 dead since 2009.
Unable to put an end to the violence thus far, Nigerian President Goodluck Jonathan has set up a panel to study how an amnesty could be offered to Boko Haram. It remains unclear, however, whether the group would accept any such proposal.
mkg,slk/jm (AFP, dpa, AP)