NIGERIA’S president has appealed for calm following reports of intercommunal violence between ethnic groups at a market in the southwestern state of Oyo. Clashes between traders from the Yoruba and Hausa ethnic groups broke out on Saturday at Shasha market in Ibadan, the capital of Oyo, the state governor's spokesman said. Most Yoruba live in southwestern Nigeria, while the Hausa are concentrated in northern states. Tensions have increased in southwestern states in recent weeks amid claims by public figures that nomadic cattle herders from the mainly northern Fulani ethnic group are carrying out violent crimes, which the pastoralists have denied.…