BAGHDAD, Iraq (CNN) -- Violence in Iraq's Basra province has dropped by 90 percent since British troops moved their base outside the provincial capital, according to British military authorities.
British forces withdrew from the center of the province's Basra city to an airport base in early September.
"Most of the violence was being perpetuated against British forces. Once we repositioned to the contingency operating base at the airport, we were no longer a target, so the level of overall violence dropped by 90 percent," Lt. Col. Derek Plews, spokesman for Maj. Gen. Graham Binns, told CNN on Friday.
"In all places you get some degree of violence, whatever the city. In Basra, there was some underlying violence happening that's still happening. But most of the violence was being perpetuated against us," he said, saying that violence "has returned to its normal level."
Plews did not provide numbers, but the observation dovetails with other examples of decreasing violence in Iraq, including statistics that show roadside bombing attacks at their lowest levels in two years.
Now that Iraqi soldiers and police are taking the security lead in Basra, they are enduring the brunt of attacks, according to Lt. Col. Nick Goulding, spokesman for Lt. Gen. William Rollo, the senior British military representative to Iraq.
Goulding, who referred to the drop in violence as "dramatic," told CNN on Friday that an official security handover to Iraqi troops is possible in mid-December.
Britain plans to decrease its troop levels to about 4,500 by the end of next month and then to 2,500 by spring.
The Iraqi south, including Basra, has not been as violent during the war as Baghdad and other regions, but the British military has had to deal with violent power struggles between Shiite militias, particularly the Mehdi Army and the Badr Brigade.
Goulding said the violent rivalry between Shiite militias in Basra has not increased in recent months as had been anticipated when British forces moved out of the city center.
Meanwhile, U.S. and Iraqi troops launched an early Friday morning raid targeting al Qaeda in Iraq militants who are thought to be involved in a deadly ambush of U.S. soldiers in May, the U.S. military said.
Lt. Col. Randy Martin, Multi-National Division Center spokesman, confirmed U.S. helicopters delivered around 600 soldiers into two villages south of Baghdad -- Owesap and Betra -- to take on militants.
He said the military believes al Qaeda in Iraq has been staging attacks from the area and has links to the May 12 ambush near Mahmoudiya, which is south of Baghdad.
Four American troops and an Iraqi interpreter were killed in that attack, and three soldiers were kidnapped. The body of one was found later and two other soldiers are still missing.
No enemy fighters were killed or captured during Friday's raid, the military said.
Earlier Friday, U.S. F-16 fighter jets dropped two 2,000-pound bombs on an island in the Euphrates River thought to be used by al Qaeda for staging attacks.
In other raids targeting al Qaeda in Iraq, troops killed two insurgents and detained 12 others. E-mail to a friend
Jennifer Deaton contributed to this report.