Armed gunmen have launched an attack on the Abu Ghraib prison in Iraq, hitting the facility with rocket-propelled grenades and mortars; a number of 500 to 1000 prisoners reportedly escaped, officials say.

The attackers hit the facility on the western outskirts of Baghdad late on Sunday night, as well as another prison in Taji, north of the capital.

The interior ministry said soldiers, police and attack helicopters had been dispatched to the prison to end the fighting and rioting by prisoners.

"The security forces in the Baghdad Operations Command, with the assistance of military aircraft, managed to foil an armed attack launched by unknown gunmen against the ... two prisons of Taji and Abu Ghraib," the ministry said in a statement late on Sunday night.

"The security forces forced the attackers to flee, and these forces are still pursuing the terrorist forces and exerting full control over the two regions," it said.

Al Jazeera's Jane Arraf, reported from Baghdad, said the attacks appeared to have been staged in an attempt to free prisoners.

Officials estimated that 500 to 1000 prisoners could escape from last night’s terrorist attack.