BAGHDAD, Dec. 19 (Xinhuanet) -- A powerful blast detonated in Iraq's holy Shiite city of Najaf on Sunday, witnesses said.

    A black plume of smoke was seen rising into the sky, they added.

    The blast took place at about 3:30 p.m. (1230 GMT) in an area that is 400 meters away from the shrine of Imam Ali in Najaf, 160 km south of Baghdad.

    The cause of the blast was not immediately clear, and there was no immediate word on casualties.

    The attack came two hours after a suicide car bomber exploded his vehicle near the main bus station in Karbala, another Shiite city located about 70 km northwest of Najaf.      

    Hospital officials said 10 people were killed and 40 others injured in that attack.  Enditem