U.S. helicopters dropped 600 troops into two villages south of Baghdad before sunrise Friday, launching an assault on militants believed to be involved in the May kidnapping of three American soldiers, the military said.

The raids took place around 4 a.m. in the villages of Owesap and Betra, about 12 miles south of the Iraqi capital.

"These are areas where we believe Al Qaeda was staging attacks, and we also believe they have ties to the May 12 attack," said Maj. Alayne Conway, spokeswoman for the Army's 3rd Infantry Division.

Three U.S. soldiers were kidnapped after their patrol was ambushed May 12 near Mahmoudiya, also south of Baghdad. Four other Americans and an Iraqi interpreter were killed in the attack, and an Al Qaeda-linked group claimed responsibility.

Two soldiers remain missing, and the body of the third was found in the Euphrates River nearly two weeks later.

On Friday, two Chinook helicopters and eight Black Hawks dropped 600 U.S. troops into the targeted area, Conway said. F-16 fighter jets then dropped two bombs on an island in the Euphrates, to "deny the enemy terrain to escape," she said.

Some 150 Iraqi soldiers also participated in the operation, Conway said. By midday Friday, there were no casualties on either side, she added.

Iraqi police said eight Al Qaeda fighters were killed separately in a Shiite village near Muqdadiyah, about 60 miles north of Baghdad. Shiite townspeople, backed by police, drove the Sunni militants out of the village and killed eight of them, police said.

Meanwhile, a top British commander in southern Iraq said attacks plunged 90 percent across the country's south after Britain withdrew its troops from the main city of Basra.

The presence of British forces in downtown Basra, Iraq's second-largest city, was the single largest instigator of violence, Maj. Gen. Graham Binns told reporters Thursday on a visit to Baghdad's Green Zone.

"We thought, 'If 90 percent of the violence is directed at us, what would happen if we stepped back?'" Binns said.

About 500 British troops moved out of a former Saddam Hussein palace at Basra's heart in early September, joining some 4,500 at a garrison at an airport on the city's edge. Since that pullback, there's been a "remarkable and dramatic drop in attacks," Binns said.

Binns said the drop included attacks on U.S. and Iraqi forces, which represented the bulk of overall violence there.

Last spring, British troops' daily patrols through central Basra led to "steady toe to toe battles with militias fighting some of the most tactically demanding battles of the war," Binns said. Now British forces rarely enter the city center, an area patrolled only by Iraqis.

The majority of attacks now target Iraqi forces, but even that figure has decreased since the intense battles of May and June, Binns said.

In mid-December, British forces are scheduled to return control of Basra province back to Iraqi officials — officially ending Britain's combat role in Iraq.

With an overwhelmingly Shiite population, Basra has not seen the level of sectarian violence that has torn Iraq apart since the February 2006 bombing of a Shiite shrine north of Baghdad.

But it has seen major fighting between insurgents and coalition troops, as well as between Shiite militias vying for control of the city and its security forces.

British officials expected a spike in such "intra-militia violence" after they pulled back from the city's center, and were surprised to find none, Binns said.

Also Friday, the chairman of a key committee in Iraq's parliament said a draft law that would allow former Saddam followers to hold government jobs is unconstitutional.

The new law was submitted to parliament this week. If approved, it would relax curbs on former Baath Party members — a key demand of the U.S. and Sunni Arabs.

But the head of parliament's "de-Baathification Committee," Falah Hassan Shanshal, said Friday that language in the draft law violates the constitution. Among other things, Shanshal said the law might open government jobs to low-ranking Baath members who had still committed crimes and would trigger a backlash among Iraqis — especially Shiites.

Violence continued Friday, with one civilian killed by a roadside bomb outside a motorcycle shop in central Baghdad, police said.

Four others were wounded by the blast and transferred to a nearby hospital, they said. Some damaged was sustained to buildings next to the shop.

About an hour earlier, gunmen opened fire on the same spot, wounding one civilian, police said.

The attacks took place near the Abdul-Qadir al-Gailani mosque, a Sunni shrine in central Baghdad's Sinak district, a mixed area.

Police also found the bodies of two men, both with bullet wounds to the head, dumped in a barren area near Sadiyah, 60 miles north of Baghdad. The two were identified as brothers who had disappeared Thursday evening in the same town, police said.