Ahmed Khalaf Falah, a farmer, has told The Associated Press that he witnessed seven masked gunmen seize the soldiers near Youssifiyah, about 12 miles south of Baghdad.

Iraqi Foreign Minister Hoshyar Zebari said Sunday that insurgents had taken the soldiers prisoner. "Hopefully they would be found and released as soon as possible," he said on CNN's "Late Edition."

Secretary of State Condoleezza Rice said there was "great concern" over the missing soldiers.

"The American military has made very clear that they are going to do everything possible ... to try and find them," she told reporters.

Kidnappings of US service members have been rare since the 2003 US-led invasion, despite the presence of about 130,000 forces.

US troops patrol only in convoys. Foot patrols, while common in parts of Iraq during 2003 and 2004, have become rare because of roadside bombs, snipers and ambushes.

The last US soldier to be captured was Sgt. Keith M. Maupin of Batavia, Ohio, who was taken on April 9, 2004 after insurgents ambushed his fuel convoy. Two months later, a tape on Al-Jazeera purported to show a captive US soldier shot, but the Army ruled it was inconclusive.

Six soldiers, including Pvt. Jessica Lynch, were captured in an ambush in southern Iraq in the early days of the war - March 23, 2003. Lynch was rescued April 1, 2003, the others 12 days later.

The Mujahedeen Shura Council did not make threats or demands in the abduction of Pfc. Kristian Menchaca, 23, of Houston, Texas, and Pfc. Thomas L. Tucker, 25, of Madras, Ore., saying only that "we shall give you more details about the incident in the next few days, God willing." Spc. David J. Babineau, 25, of Springfield, Mass., was killed in the attack on the checkpoint at a canal crossing near the Euphrates River.

All three were from the 101st Airborne Division based at Fort Campbell, Ky.

The Shura Council taunted the military by saying that it had "launched a campaign of raids using armor and equipment, in the region around the incident, but the army of 'the strongest nation in the world' retreated in defeat and disgrace."

The separate statement on the Russians demanded that Moscow withdraw from war-torn Chechnya within 48 hours and release Islamic militants from its prisons or "face the consequences."

The Russian Foreign Ministry called for their immediate release and said "the abduction of citizens of a country that is energetically helping to restore peace in Iraq" cannot be justified.

In Baghdad, where a two-day surge in violence ended a three-day lull, Prime Minister Nouri al-Maliki sought to regain the initiative by sending tanks, armored vehicles and thousands of army troops into the city.

In the Sunni Arab neighborhood of Azamiyah, two Iraqi tanks were deployed in the main square, a short distance away from the Grand Imam mosque, Iraq's holiest Sunni site. Iraqi armored personnel carriers and newly acquired U.S.-made Humvees were also patrolling the city's most dangerous neighborhoods on the western bank of the Tigris.

Iraqi army troops also patrolled on foot and in many areas they manned positions behind concrete barriers and sandbags.

In the troubled western Baghdad neighborhood of Jamaa, Iraqi soldiers manned checkpoints from behind concrete blast barriers to defend against suicide car bombers.

Nearly 500 detainees were released Monday as part of al-Maliki's national reconciliation effort. Most are Sunni Arabs and al-Maliki's plan to release 2,500 of them by month's end aims to reach out to the community.

In a fresh blow to the image of American troops in Iraq, the US Army charged three soldiers in connection with the deaths of three Iraqi men while they were in military custody on May 9 during an operation near Thar Thar Canal in Salahuddin province north of Baghdad.

The soldiers belonged to the 3rd Brigade Combat Team, 101st Airborne Division, the military said in its announcement Monday. At least 15 service members have been convicted on a range of charges in the deaths of Iraqi civilians since the beginning of the war.