On Monday, the sound of crashing mortars and machine-gun fire could be heard at the western and northern entrances of Najaf from about 4am (0100 GMT), as US helicopters circled overhead.
Artillery and tank fire, backed up by air power, battered the centre of the city. Shia leader Muqtada al-Sadr's al-Mahdi Army fighters are still hunkered down in positions near the city's sacred Imam Ali shrine and the vast Najaf cemetery.
Smoke was seen rising from several locations near the city's ancient cemetery, the scene of close-quarter fighting in recent days.
In the Baghdad stronghold of al-Sadr, the US occupation military said four mortar bombs were fired at the district council hall in the sprawling slum of Sadr City from about 8am (0400 GMT).
Missing the hall, they slammed into neighbouring houses, a spokesman said. Further explosions could be heard coming from the northeastern neighbourhood in the subsequent hours.
Al-Mahdi fighters hunkered down
in their positions
A spokesman for al-Sadr said only 15 fighters had been killed and 35 wounded, the majority from cluster bombs.
But the US occupation military claims it has killed more al-Mahdi fighters in Najaf since the fighting started on Thursday.
In the south, a spokeswoman said a British base came under mortar fire twice on Sunday night and that numerous British patrols came under small-arms fire and rocket-propelled grenade attacks in Amara.
A series of mortars were also fired at an occupation forces' building in the city, where the al-Mahdi Army has attacked foreign troops previously. No casualties were reported in any of the incidents.