From early Wednesday, heavy US artillery fire followed fighter plane missile attacks, devastating neighbourhoods in the historic heart of the central city.

As the US campaign lessened in the hot afternoon sun, frightened residents barricaded themselves indoors, determined to bear the brunt of the crippling summer heat rather than wander the empty streets.

Those who did venture out, or peep through the broken windows or blasted door frames, could barely disguise their fear.

"It was the heaviest attack in many days especially the first during daytime," said Ali Jasim, a 36-year-old civil servant holed up in one house.

"Not only did airplanes drop missiles, but Apache helicopters fired at suspected militiamen in our area and tanks crawled all over the place firing at whatever they saw. All the three at the same time."

One young man who was standing outside his house shot by soldiers from the helicopter, he said.

"You can see his blood all over that corner in the mud," Jasim said pointing.

Shiite militia holed up in the neighbourhood fought against the American and Iraqi soldiers.

"The militia has a lot of snipers around. They shot at a lot of Iraqi soliders who have been moving around in the area since Tuesday," he said.

Hundreds of heavily-armed Iraqi national guardsmen and US marines had fanned out across the Old City around the shrine late Tuesday.

But the Iraqi security troops were invisible in the afternoon. Some residents thought they would return later for another overnight assault.

Instead, US tanks crawled through the streets and Humvees were stationed at various intersections. Thick black smoke rose from a nearby residential block.

"The worst thing is that all entries to the city were blocked. Many of us who have families and had gone out early in the morning were worried as they could not get back to their homes," said Sayed Haider al-Yasiri.

Guiding an AFP correspondent to a nearby street corner, Yasiri pointed out an unexploded bomb lying outside a shuttered shop.

"Look at this and see what has happened out here. Imagine if a child picks it up," he said, dressed in a white robe and chewing on a mouthful of tobacco.

Scared residents of the Old City, who have born the brunt of the battle since fighting first flared three weeks ago, were Wednesday helpless and angry with the US military.

"We want to get rid of the militia, but not in this way. Such heavy pounding would destroy whatever is left of our homes," said Mohammed, a taxi driver.

"Why can't there be a peaceful solution to this whole issue?"

The mute spectators to the fight are dozens of those broken lamposts, hanging electric wires, spent cartridges and glass splinters, gaping holes and the fear etched on people's faces.

"It is still OK to walk closely by the side of the walls in some of the blocks of the city, but please do not go to Medina Street if you love yourself," said one young man, where rapid firing continued as US planes hovered overhead.

"There could be fresh assault at night also. Please go back before the roads are blocked again," the young man said.

WAR.WIRE