Baghdad (AP): Shia militia fighters stormed a state TV facility in the southern city of Basra on Sunday, forcing Iraqi military guards surrounding the building to flee and setting armored vehicles on fire.

No casualties were reported but the daring raid illustrated the stark challenges facing Prime Minister Nouri al-Maliki's government in its crackdown against militia violence in the oil-rich area.

The strength of the resistance to the week-old offensive has taken the U.S.-backed government by surprise, forcing it to come up with a new tactical plan targeting several Mahdi Army strongholds, a government official said.

The official, who was in Basra but spoke on condition of anonymity because he wasn't authorized to release the information, said al-Maliki also had brought in reinforcements and appealed to local tribal leaders to help secure the area.

The prime minister, himself a Shia, has called the fight ``a decisive and final battle'' and vowed to remain in Basra until government forces wrest control from militias, including the Mahdi Army that is loyal to radical cleric Muqtada al-Sadr.