A Nigerian senator and several other people were killed on Sunday when gunmen attacked a mass burial for 63 victims of violence the previous day in ethnically mixed Plateau state, a government official said.
Saturday's clashes between security forces and armed Fulani herdsmen erupted after the military said they intervened when fighting broke out between Fulani migrants and indigenous tribes in the Barkin Ladi district in Plateau.
A spokesman for the Fulani said the military opened fire on them because the government favours indigenous tribes.
Plateau state government imposed a dusk-to-dawn curfew on Sunday in Barkin Ladi and three other government zones.
The Islamist sect Boko Haram has claimed several suicide bomb attacks this year on churches in Jos, the Plateau capital, prompting a Christian backlash against Muslims. There was no sign Boko Haram was involved in this weekend's fighting.
Plateau is in the "Middle Belt", where the largely Christian south meets the mostly Muslim north. It has for years been a tinderbox of ethnic and religious rivalries over fertile land and power between local people and migrants from other areas.
Senator Gyang Dantong of the ruling People's Democratic Party and a state lawmaker were among several people shot dead while attending the burial, officials said, adding that they had no details on how many people were killed.
Burials were also under way in other parts of the state and the final death toll is likely to be higher.
"Tragedy. Serving Senator died following Fulani attack on mourners at a mass burial of 63 victims of a Fulani attack on over 9 villages the previous day," said Istifanus Gyang, security adviser to the Plateau state governor.
Tit-for-tat killings between religious and ethnic groups have run on for several days in Plateau in the past. In January 2010, more than 300 people were killed and in November 2008 over 700 were killed in a week of fighting.
President Goodluck Jonathan sacked his defence minister and national security adviser last month, saying the country needed "new tactics" to fight "terrorism". He gave few details.
A statement from the presidency on Sunday said the death of Dantong was "cruel and regrettable" and that security agencies had been ordered to track down his killers.
Security experts believe Boko Haram's attacks on churches in central and northern Nigeria are an attempt to provoke a wider religious conflict inside Africa's biggest oil producer.
But much of the violence in Jos is a result of long-running ethnic tensions and local political power struggles, and is not instigated by Boko Haram.
Boko Haram has killed hundreds this year in its insurgency against Jonathan's government. The sect wants to carve out an Islamic state in the north of Africa's most populous nation.