Nigeria's army says its soldiers have been given permission to shoot to kill to maintain order in the city of Jos.
"We are ordered to protect civilians and quell violence by any means necessary," military spokesman Capt Charles Ekeocha told the BBC.
A series of killings and bomb attacks over Christmas and New Year are thought to have resulted in more than 100 deaths so far in the central city.
Jos is a flashpoint of tension between Hausa Muslims and Berom Christians.
It sits on the faultline between Nigeria's north and south.
Capt Ekeocha publicly warned community leaders that the military would fire on anybody burning homes, churches and mosques or carrying out lynchings and attacking civilians.
An election official was killed and his body set on fire by an angry mob - one of three people killed in a riot on Monday - as people tried to register to vote.
Jos has experienced repeated outbursts of bloodletting: In deadly riots along city interfaces and in carefully planned attacks on remote villages.
The exact number killed this year alone is uncertain, with officials saying about 100 people died.
But a Christian group - the Stefanos Foundation - is questioning that.
It has just published graphic photographs of what it says are more victims of violence.
Their report shows scores of stiffened and charred corpses littering the ground in the aftermath of riots on 8 January.
The Stefanos Foundation says the Nigerian authorities buried those bodies immediately, and that the true scale of the killings is being concealed because the authorities fear sparking reprisals.
The police commissioner in Jos told the BBC he had not seen the photographs.
''On each occasion we have fully disclosed the facts that we are aware of in press conferences and we are not concealing any figures," the commissioner said.
''However, we will study the photographs of these new corpses if they are handed to us."