KARACHI: Police killed seven "unruly inmates" and wounded 20 more during an operation to prevent a jail-break in a prison in Hyderabad, officials said Wednesday.

"At least seven inmates have been shot dead and 20 others wounded after an armed clash with the police late Tuesday night in Hyderabad prison," Abdul Qadir Thebo, inspector-general of prisons for southern Sindh province told AFP.

"Nine of our officials were also injured in the exchange of fire." Thebo said armed prisoners clashed with police after they were asked to surrender weapons, mobile phones and other prohibited items they had been using freely, and return to their cells.

"Some of the inmates had weapons and fired shots on the policemen, forcing

a retaliation."

He said the prisoners had "virtual control" of the prison and had been planning a jail-break.

"We have ordered an inquiry to find out how the banned articles entered the prison in first place," Thebo added.

He said the bodies and the injured had been moved to a hospital in

Hyderabad.