Prison workers say at least 10 inmates and a prison officer have been shot and killed in an attempted jailbreak in southeastern Nigeria, though police say they only shot into the air.

Local newspapers reported that one prisoner disarmed a guard, killed him and wounded two others in Thursday's riot at Abakaliki Prison in Ebonyi state.

A warden and a cook said they saw between 10 and 14 inmates killed, speaking on condition of anonymity for fear of losing their jobs.

Police spokesman George Okafor says riot police fired into the air and used tear gas. He denies anyone was killed.

The incident comes the same week the Prisons Service dismissed 23 officers for allegedly colluding in jailbreaks from two prisons.