The massive search for three missing U.S. soldiers believed to have been kidnapped by Al Qaeda-linked insurgents entered its seventh day with the commander in charge of the search mission issuing a statement.

Col. Michael Kershaw, the commander of the 2nd Brigade Combat Team, 10th Mountain Division who was overseeing the mission, said the teams were talking to local Iraqis, hoping to find information that would lead them to the soldiers.

Complete coverage is available in FOXNews.com's Iraq Center.

"Everyone is motivated and knows the importance of finding the soldiers," he said in a statement from Quarghuli, a village 12 miles south of Baghdad where a May 12 ambush killed four U.S. soldiers and an Iraqi, and left three American troops missing.

On Thursday, U.S. officials expressed cautious optimism that the missing soldiers were still alive even as troops drained canals and questioned children in the search. FBI agents and Australian forensic experts also took part in the operation.

Diyala province — with its mixed Shiite and Sunni Muslim population — has been the scene of frequent sectarian violence as well as attacks by anti-U.S. insurgents. The U.S. military has sent 3,000 additional forces to try to tame the violence.

Meanwhile, about 50 suspected insurgents attacked a U.S. base in the center of a city north of the capital Friday, sparking a battle with U.S. soldiers and helicopters that killed at least six militants, the Iraqi army said.

The fighting took place in Baqouba, a Sunni insurgent stronghold that has seen a recent spike in violence largely blamed on militants who fled a 3-month-old security crackdown in Baghdad.

At 7 a.m., the day of rest in mostly Muslim Iraq, about 50 suspected insurgents opened fire on a U.S.-Iraqi base in downtown Baqouba, 35 miles northeast of Baghdad, wounding two Iraqi soldiers, an Iraqi army officer said.

U.S. forces and helicopters responded at 7:30 a.m., killing at least six insurgents, the Iraqi army officer said on condition of anonymity because he is not authorized to speak to the media.

Residents said the fighting sent smoke billowing up from neighborhoods in the area.

One resident, who spoke on condition of anonymity for fear of reprisals from militants, said he heard heavy machine gun fire and then men shouting "Allahu Akbar," or God is great in Arabic. Others said they saw U.S. tanks and armored vehicles driving through the street, while aircraft flew overhead.

The base was set up two months ago in a three-story city office building that was abandoned because of the violence in the area, the Iraqi officer said.

The U.S. military had no immediate comment on the incident.

Baqouba and the rest of the Diyala province have been hit by a string of attacks this week.

Gunmen hijacked a bus in Baqouba and took 23 passengers hostage, a car bomb exploded near a market in a Shiite village, killing at least 32 people, and five civilians were killed execution style in broad daylight in the city by gunmen who appeared to be accusing them of collaborating with the U.S.-led forces.

The search for the three missing U.S. soldiers feared captured by Al Qaeda has involved about 4,000 U.S. troops and 2,000 Iraqis.

The soldiers were captured in an ambush on their two-vehicle patrol. Maj. Webster Wright, a U.S. military spokesman, said the soldiers had been in position for eight to 12 hours when a large number of insurgents crept up on them through the foliage, cut concertina wire and attacked from all directions.

The attack appeared aimed at capturing soldiers, because there were signs that a getaway car was used, he said.

About 900 people had been questioned so far and 36 were detained, Webster said. U.S. forces also dropped 250,000 leaflets over the area.

Lt. Col. Randy Martin, a U.S. military spokesman, said searches had produced a number of leads that "point to the fact that these men are still alive."

"There are also reports to the contrary. But we have an obligation to follow on every intelligence tip," Martin said. "There is cautious optimism that in fact these soldiers can be found alive," Martin said. "That's what we pray for, that's what we hope for."

Meanwhile, Army officials have identified the fourth soldier killed Saturday in the ambush, a newspaper reported late Thursday. Sgt. Anthony J. Schober, 23, of Reno, Nev., was identified by DNA testing, the soldier's relatives told the Reno Gazette Journal. Three other soldiers killed in the ambush had previously been identified.

As the search for the missing soldiers was under way Thursday, three American soldiers were killed and another was wounded in a roadside bombing south of Baghdad, the U.S. military reported. The statement provided no more details, and it was unclear if the victims were part of the search.

Meanwhile, the U.S. military said it detained six suspected insurgents Friday during raids in northeast Iraq. It accused them of being members of a cell that imports powerful weapons from neighboring Iran, and brings Iraqis to Iran for training as insurgents.

On May 28, talks between U.S. and Iranian officials are scheduled to begin in Baghdad to discuss the security situation in Iraq. Washington has often accused Iran of arming insurgents and militias.