Akesan, the central market in Oyo town was shut Monday morning, as rival gangs unleashed violence on the market and adjoining areas.
The violence, the latest in what residents say has now become a regular occurrence, was between dreaded rival gangs known as Agunpopo and Ilaka.
Guns, bottles, machetes and other dangerous weapons were freely used in the fighting.
Those familiar with the immediate cause of the clash told PREMIUM TIMES the group from Ilaka had gone to Agunpopo's carnival on Saturday night to "cause trouble".
The reprisal attack by the Agunpopo group on the Ilaka gang on Monday morning has now effectively shut down Akesan market, the usual battlefield of the two camps, traders and security officials said.
Traders were prevented from opening their shops on Monday.
Residents are now asking road users to divert from all roads leading to the market, including Apinni, Kanga, Garage and Palace roads.
The actual number of casualties cannot be immediately ascertained, but a witness simply identified as Rasaq said one person was killed.
The Oyo State Police Command could not be reached immediately for comments.