Moscow  - Four Russian prisoners died after being severely beaten by guards in retribution for attacking staff at a jail in the Urals city of Chelyabinsk, the regional prosecutor's office said Monday.

The four men, convicted of drug trafficking, "behaved agressively" in the convoy to the prison after their sentencing, calling on their fellow prisoners to rise up against the guards, local officials said.

The prosecutor's office said the convicts injured five guards, attacking them with self-fashioned blades and other contraband weapons.

An investigation has been opened into the conduct of the guards who retaliated with bludgeons. The men died later in the evening in separate isolation wards, news agency Interfax quoted authorities as saying. (dpa)