A deafening salvo of nearly 40 rounds of air-launched cannon fire was heard across Baghdad late on Tuesday in a further sign the US military is revising its methods to combat the mounting attacks on occupation troops.

A US military spokesman said the firing was connected to Operation Iron Hammer, a massive military offensive launched in and around Baghdad on 12 November, and targeted "downtown Baghdad".
 
"The explosions you have heard are part of Iron Hammer," said Captain David Gercken, spokesman for the 1st Armoured Division which is carrying out the offensive.

"They are fired from aerial platforms. The weaponry used is 105mm cannons," he said, without specifying whether they were launched by warplanes or helicopters.

Targets

Another US spokesman said the bombardment targeted three
locations near the occupation authority's sprawling, heavily fortified city centre compound.

Air support has been called many
times north and west of capital

It also houses the headquarters of the US-installed Iraqi interim leadership and has been a regular target for rocket fire in recent weeks.

"We are firing at three designated targets near the Green Zone," said Captain Aaron Hacok using the military's codeword for the compound.

"We have received no enemy heavy artillery or mortar fire and I have no report of small arm fire." 

'Whatever necessary'

In recent days, US commanders have taken off the gloves in their battle with the resistance to the US-led occupation, resorting to air strikes and heavy artillery against the safe houses and arms caches of insurgents.

Air support has been called in several times north and west of
the capital, but Tuesday's was only the second reported incident in Baghdad itself.

Earlier on Tuesday, a senior US commander defended the new
get-tough tactics. 

"Now it is no holds barred. We use whatever weapons that are necessary to take the fight to the enemy," said Major General Charles Swannack, whose 82nd Airborne Division patrols Al-Anbar province west of the capital, a hotbed of anti-US insurgency.