Some inmates being conveyed to court were on Thursday released by some protesters along the Benin-Auchi highway.
The protesters, comprising tipper drivers and youths, were kicking against the killing of one Federick, popularly known as Original, by a policeman deployed to provide security for expatriates in a construction firm.
Sources said Federick was shot at a close range after an argument with the policeman whose identity was yet to be ascertained.
It was gathered that the protest began after news filtered in that Federick had died.
The protesters barricaded the Benin-Auchi highway at the by-pass axis.
Several vehicles were destroyed by the protesters as motorists sought alternative routes.
A vehicle conveying prison inmates to court refused to turn around and was attacked by the protesters.
Prison warders in the vehicle were attacked.
One of the prison officials managed to run into the bush with wounds and was rescued by some residents.
He was taken to a private hospital.
Spokesman for the Nigeria Correctional Service, Aminu Suleiman, who confirmed the attack, said details were still sketchy.
Suleiman said the officials were going for official duty when they were attacked.
A source in the area said the Warden was found inside the bush with a deep injury in his hand and bleeding seriously.
Security personnel were said to have been deployed to the area to search for the runaway inmates.
Police spokesman, DSP Chidi Nwabuzor, could not be reached for comments.