Up to 2,000 prisoners, many of them Taliban and Al-Qaeda members, have taken control of parts of a notorious high security jail in the Afghan capital, Kabul.
Seven people are reported to have killed in the uprising and the jail is now surrounded by hundreds of Afghan security forces as well as US and NATO troops.
Some reports said the uprising developed into an escape attempt, with prisoners trying to get over the walls.
At least 30 inmates have been wounded after riots prompted wardens to open fire.
The prisoners are understood to be refusing to hand over the injured for treatment.
An official said that certain inmates have taken some female prison guards hostage and are apparently threatening to kill them if their demands are not met.
The riot at the prison, some 10km from the centre of Kabul, erupted when guards distributed new prison uniforms which some inmates refused to wear.
Pul-e-Charkhi is Afghanistan's biggest prison and holds more than 7,000 prisoners, about 600 of them suspected militants.
Fires at the facility, which were caused when prisoners set mattresses and clothes alight, have since been brought under control, although it is reported that rioters have broken through walls separating different sections of the block in an apparently organised revolt.
Police and up to 150 soldiers have put a security cordon around the area.
