U.S. bombers and fighters have launched a massive air assault on what are being described as al-Qaida in Iraq safehouses on the southern outskirts of Baghdad. VOA's Deborah Block has the story from the Iraqi capital.

During the 10-minute bombardment, 18,000 kilograms of explosives were dropped on 40 targets described as terrorist safehouses in the Arab Jabour area south of Baghdad.

In a statement, the U.S. military said the amount of explosives used in the attack was one of the largest since the war began in 2003. The attack is part of an ongoing operation against al-Qaida in Iraq insurgents that has been launched by U.S. and Iraqi forces.

U.S. commanders say the insurgents have been mostly pushed out of Baghdad and western Anbar province, but are now entrenched in other parts of the country, including volatile Diyala province, just north of Baghdad.

On Wednesday nine American soldiers were killed as part of a new security operation that was launched this week. Six died in an explosion as they entered a booby-trapped house.

Major General Mark Hertling, commander of the coalition forces in northern Iraq, said 20 to 30 al-Qaida in Iraq fighters were killed in Diyala during the first two days.

"And as the Iraqi army gets stronger and the Iraqi police stand up, there is no place for these folks to go," said General Hertling.

He said the militants in Diyala were likely to move their operations elsewhere as the troops advanced but would eventually be pinned down.

"We're tracking some of the leaders," he said. "And we're also tracking where some of the leaders have gone. We're continuing to pursue [them]."

U.S. commanders say an increase in the number of volunteer security patrols, known as concerned local citizens, has also put the insurgents on the defensive. These thousands of volunteers across Iraq are actually paid a small salary by the United States to guard their neighborhoods. The American military says they have helped reduce the number of insurgent attacks by more than half since June.