The explosion that wounded the soldiers took place about 3 p.m., the U.S. command said, without providing further details.
Roadside bombs are a major threat to U.S. troops across the country. A review of Pentagon casualty reports shows that of 39 deaths in January that the Army attributed to hostile action, 23 involved attacks with homemade bombs, which the military calls "improvised explosive devices."
In Fallujah, residents said Friday that two men suspected of having been informants for the Americans were slain by insurgents. The killings, which occurred late Thursday and early Friday, came after pamphlets were circulated in the area west of Baghdad warning Iraqis against cooperating with the occupation force.
In other developments:
Separately, scores of well-wishers gathered Friday near the house of Iraq's most powerful Shiite cleric, Grand Ayatollah Ali al-Husseini al-Sistani, in the holy city of Najaf to check reports of an attempt on his life. They were met by security guards who told them that their spiritual leader is safe and accounts of a failed assassination were false.
Arab media reported the attempt on al-Sistani's life Thursday in Najaf. But details varied widely, and the report has been denied by two bodyguards, the ayatollah's political allies and by U.S. officials.
Hassan al-Jarah, a student who visited al-Sistani's office Friday, said he did not notice anything wrong. "It seems very much business as usual," he told The Associated Press.
Al-Sistani is not known to have left his modest house in the center of the city since last April, and receives very few visitors except other clerics and students.
The raids around Saddam's hometown of Tikrit were targeting Iraqis suspected of involvement in attacks on U.S. troops and helicopters, said Lt. Col. Steve Russell, a battalion commander in the 4th Infantry Division.
"The individuals are closely tied to the Saddam family and the former regime. They represent some of the last of the main network that we have been targeting for many months," Russell said without providing details.
Also Friday, about 800 Iraqis demonstrated in Khaldiyah, west of Baghdad in the Sunni Triangle, to demand that a dusk-to-dawn curfew be lifted and Iraqis detained by U.S. forces be released. The curfew was imposed late last month after a roadside bomb killed three American soldiers.
American forces are tracking a shadowy militant group that claimed responsibility for Sunday's back-to-back suicide bombings at Kurdish political offices in the northern city of Irbil. The attacks killed at least 109 people, including senior Kurdish politicians who were strong U.S. allies.
A statement from a group calling itself the Ansar al-Sunna Army said it targeted the "dens of the devils" because of the Kurds' ties to the United States.
The U.S. military believes Ansar al-Sunna is a splinter group of Ansar al-Islam, allegedly linked to the al Qaeda terrorist network. The claim could not be confirmed.
In Irbil, Muslims clerics used their Friday sermons to denounce the attacks against the Patriotic Union of Kurdistan and the Kurdistan Democratic Party.
"Islam doesn't call for killing those who are unarmed...Those who committed these two crimes do not belong to Islam regardless of whatever names they call themselves," imam Suleiman Abdullah told hundreds of worshippers in the Mustafa Naqshabandy mosque.
Police Capt. Abdul Haji al-Kazim, a member of a security force set up last year to protect Najaf's clerics following the assassination of an important Shiite clergyman, said he was on duty all day Thursday and noticed nothing unusual.
A U.N. election expert, Carina Perelli, was in Amman, Jordan on Friday. U.N. officials refused to confirm her presence or say why she was there. However, it appeared she was en route to Baghdad to head a mission to determine if Iraq can hold early elections, which are being demanded by the majority Shiites.