A roadside bomb killed three American soldiers and an interpreter north of Baghdad, the U.S. military said Wednesday, and Iraqi police reported 14 Shiite gunmen were arrested after fighting south of the capital.

In Baghdad, meanwhile, American soldiers using specially trained dogs sifted through the wreckage Wednesday of an office in Sadr City where a bomb killed 10 people, including four Americans working to restore local government in the former Shiite militia stronghold.

The Iraqi Defense Ministry spokesman suggested that Iraqi officials — and not the Americans — were the main target.

At least 25 service members have died this month, with eight deaths coming since Friday. May's death tally of 19 was the lowest monthly toll of the Iraq conflict.

Also Wednesday, U.S. soldiers in Baghdad killed three gunmen who fired on an American convoy that had stopped along the side of the road just west of the city's airport, the U.S. said. No further details were released.

The roadside bombing occurred about 10:45 p.m. Tuesday in Nineveh province, where al-Qaida in Iraq and other Sunni extremist groups remain active. The U.S. statement contained no further details.

Their deaths brought to at least 4,109 the number of U.S. military members who have died in the Iraq war since it began in March 2003, according to an Associated Press count.

The fighting in the south broke out before dawn near Nassiriyah, 200 miles south of Baghdad, as Iraqi forces were conducting house-to-house searches for Shiite militants.

Nassiriyah police chief Brig. Gen. Sabah al-Fatlawi said 14 suspects had been arrested but that sporadic clashes were continuing.

The area is a stronghold of the Mahdi Army of anti-U.S. cleric Muqtada al-Sadr and has been plagued by power struggles between rival Shiite factions — some with close ties to the Shiite-led national government.

Internal Shiite rivalries may have been behind Tuesday's deadly blast inside the district council building in Sadr City, al-Sadr's Baghdad stronghold.

The bomb went off inside a councilman's office ahead of an election to choose a new chairman of the council.

Defense spokesman Maj. Gen. Mohammed al-Askari said a preliminary investigation indicated that the Iraqi council members were the main target of the blast.

"The presence of the American forces and embassy employees was by chance," al-Askari said. "Chance played a role in the casualties among the Americans."

The council's acting head, Jawad al-Itabi, said American investigators were searching the building Wednesday along with sniffer dogs looking for clues. He said 12 people were being detained for questioning, including 10 security guards.

Two of the U.S. dead were soldiers, the military said. The U.S. Embassy said the dead American civilians included one State Department and one Defense Department employee.

An Italian of Iraqi origin who was working as an interpreter for the Americans also was killed, according to the Italian Foreign Ministry.

The State Department identified one of the slain Americans as Steven L. Farley of Guthrie, Okla. He was believed to be the first member of a provincial reconstruction team to be killed in Iraq.

Farley's son, Brett, told The Associated Press on Tuesday that his father feared the situation could become dangerous after the council ousted a Sadrist member.

"It was today that they were scheduled to vote on electing a new chairman, a pro-democracy chairman, and he told me pointedly that it was the biggest moment that they had faced over there," Brett Farley said. "He fully understood what the risk was, but he was willing to bear it."