The "Screaming Eagles" began the third day of their campaign to secure the areas south and north of the Shiite Muslim holy city by sending in another battalion of Apache attack helicopters to support infantry troops, division Aviation Brigade commander Colonel Greg Gass told AFP.

Gass said the Apaches flew out early Tuesday to join a battalion of the smaller, less powerful Kiowa Warrior helicopters south of Najaf.

The brigade's 3rd Battalion of Apaches resumed flights north of Najaf to support 101st infantry troops who were fighting an unidentified Iraqi mechanized division, Gass said.

The 101st began its campaign around Najaf on March 30, with the primary aim of securing the area for communication and supply lines in the US military's push towards Baghdad.

Najaf and Karbala, another Shiite pilgrimage city a further 80 kilometres (50 miles) closer to Baghdad, are vital to the US forces because important highways lead from there to the capital.

Gass said he had no reports of the outcome of Tuesday's fighting.

In Monday's clashes, Gass said the 3rd Battalion Apaches destroyed a "battalion's worth" of Iraqi soldiers and S-60 57mm anti-aircraft weapons, without going into specific numbers.

A statement from US Central Command's headquarters in Qatar said that several Iraqis had been killed on Monday.

"The 101st Air Assault Division conducted aggressive patrols northwest and south of Najaf, which resulted in the capture or defeat of one 120mm mortar, four weapons caches, several enemy KIAs (killed in action) and approximately 20 enemy prisoners of war," said the statement.

Gass described the combat as the heaviest his forces had been involved in since the start of the war on March 20.

"They fought pretty hard from first light (into the afternoon)," Gass said, adding eight Apaches sustained various levels of damage.

"Eight aircraft were hit anywhere from just a hole in the rotor to significant tail damage," Gass said.

Gass and other 101st officers said that much of the small arms fire that had struck the helicopters orginated from behind houses and other buildings.

Centcom also said that further north near Karbala members of the 3rd Infantry Division (3ID) attacked enemy positions in quarries, killing several more Iraqis and taking around 30 prisoners.

"At one point the brigade came under ineffective and uncoordinated enemy artillery fire which was suppressed with radar-directed multiple launch rocket system counterfire," it said.

Further attacks by the 3rd Infantry Division "resulted in the destruction of two 57mm air defence artillery systems, two armoured personnel carriers, one artillery piece, nine technical vehicles, several enemy KIAs and approximately 30 enemy prisoners of war."

WAR.WIRE