Militants unleashed attacks in a northeastern Iraq city that left four people wounded, officials said Tuesday, as the country hosted U.S. Defense Secretary Donald H. Rumsfeld (search), a leading architect of the war.

Gunmen opened fire late Monday on a police patrol in the city of the city of Kirkuk, injuring two members of the security service, police Brig. Sarhat Kadier (search) said.

Attackers also placed a bomb in the undercarriage of a doctor's car, but the device exploded as the physician entered a Kirkuk store to buy bread, sparing him but wounding two nearby civilians, Kadir said. It wasn't known why attackers targeted the doctor.

Kirkuk is 180 miles north of Baghdad -- where Rumsfeld arrived before dawn on Tuesday for his second visit in three months.

The visit by Rumsfeld, who helped design the U.S.-led March 2003 invasion and troubled occupation since, reflected a desire to push the political and military momentum that he believes has been growing since the Jan. 30 elections for a national assembly.

Rumsfeld was expected to meet later Tuesday with Interim President Jalal Talabani (search), a former Kurdish rebel leader, and Ibrahim al-Jaafari (search), the Shiite Muslim who was designated interim prime minister last week.

En route from Washington, Rumsfeld told reporters he would press the new Iraqi leadership to avoid delays on either the political or security front at a time when U.S. troops are still being killed or wounded and billions of U.S. taxpayer dollars are being invested in rebuilding the country.

"It's important that the new government be attentive to the competence of the people in the ministries and that they avoid unnecessary turbulence," Rumsfeld said.

Some in the administration of U.S. President George W. Bush are concerned that factional maneuvering during the formation of the transitional government could undermine the counterinsurgency effort that is a key to eventually pulling U.S. troops out of Iraq.

"Anything that would delay that or disrupt that as a result of turbulence or incompetence or corruption in government would be unfortunate," Rumsfeld said.

Late Monday, the U.S. embassy in Iraq announced the kidnapping of an American citizen.

A spokesman said the American contractor, who was working on a reconstruction project, had been abducted around noon Monday. The spokesman didn't release the contractor's identity or other details, but said the abductee's family had been informed.

In Samarra, a troubled city 60 miles north of Baghdad, a pickup truck blew up Monday near a U.S. patrol, killing three civilians and wounding more than 20 others, including four U.S. soldiers, officials said. One soldier was evacuated for medical treatment, and the others were treated and returned to duty, the U.S. military said.

Loudspeakers urged residents to donate blood as the wounded poured into the hospital. Most of the injured were women and children, hospital official Abdul Nasir Hamid said. The incident was in the Sunni Triangle, a stronghold of Iraq's insurgency.

Early Monday, suicide bombers tried to crash two cars and a fire truck into Camp Gannon in the western desert, but "the drivers of the vehicles were stopped short of the camp by forces manning the checkpoints," a U.S. military statement said.

The vehicles exploded, wounding three Marines and three civilians and causing slight damage to the concrete barriers and a nearby mosque, U.S. officials said.

Insurgents also fired at the camp, which is in the town of Qaim near the Syrian border, and a U.S. attack helicopter destroyed a car carrying a gunman, officials said. It was unclear how many insurgents and suicide bombers were killed in the assault.

Al-Qaida in Iraq claimed to have carried out Monday's suicide bombing in Qaim.

In a small victory against a spate of kidnappings targeting Iraqis and foreigners, a Defense Ministry official said Monday that Iraqi security forces arrested a man who claimed responsibility for last year's kidnapping of two French journalists.

The hostages, Christian Chesnot and Georges Malbrunot, were released in December after four months in captivity.

Iraqi army soldiers captured Amer Hussein Sheikhan (search) in the Mahmoudiya area on April 4, the official said on condition of anonymity. No other details were available.

Romanian President Traian Basescu's office also said three Romanian journalists kidnapped along with their guide nearly two weeks ago in Iraq were believed to be alive, and authorities were optimistic they would return home. Spokeswoman Adriana Saftoiu offered no other information.