The reports said Governor Mohammed Ali al-Hassani was on his way to Samawah, the capital of the mainly Shi'ite governorate, when his convoy was attacked. At least five of his bodyguards were wounded.
Hassani was a member of the Supreme Islamic Iraqi Council (SIIC), the largest Shi'ite party in Iraq.
A vehicle curfew was imposed on Samawah shortly after the bombing.
Earlier this month, another Iraqi governor belonging to SIIC was killed in a roadside bombing.
Al-Qadisiyah Governor Khaili Jalil Hamza and the governorate's police chief, Major General Khalid Hassan, were both killed in the attack on August 11.
The armed wing of SIIC, the Badr Organization, has been involved in a conflict with the Mahdi Army militia loyal to radical Shi'ite cleric Muqtada al-Sadr.
(Reuters, AFP, AP)