Nigerian President Muhammadu Buhari has appealed for calm after at least 10 people were killed in ethnic violence in the southern city of Ibadan.
Mr Buhari called on religious and traditional leaders not to allow ethnic or religious groups to stoke up hatred and violence against other groups.
“I appeal to religious and traditional leaders, as well as governors and other elected leaders across the country, to join hands with the federal government to ensure that communities in their domain are not splintered along ethnic and other primordial lines,” the president tweeted.
Witnesses say youths from the Hausa and Yoruba communities clashed repeatedly in a market in Ibadan on Friday and Saturday.
There have long been tensions in Nigeria between the mainly-Muslim north and the Christian-dominated south.
The governor of the South-Western Nigerian state of Oyo has also appealed for calm.
The human rights group – Amnesty International – has condemned the violence and called for those responsible for the killings to be brought to justice.
Police say they are investigating the attacks, but Amnesty International has called for an independent investigation.