BAGHDAD - An Iraqi military spokesman said Sunday that militants fleeing a security crackdown in Baghdad have made areas outside the capital "breeding grounds for violence," spreading deadly bombings and sectarian attacks to areas once relatively untouched.

The most recent strike occurred Sunday when a bomb struck a popular market in Tuz Khormato, 130 miles north of Baghdad, killing three people and wounding four. It was the second attack in the city in as many days after two Iraqis seeking work were killed in a car bombing on Saturday.

Brig. Gen. Qassim al-Moussawi promised the recent attacks would not derail the neighborhood-to-neighborhood sweep that began in Baghdad on Feb. 14.

"We are not going back. We have achieved progress and we are going to continue this progress. We need the cooperation of the Iraqi people with the Iraqi security forces. Iraqi people should give more tips about ammunition and weapons caches."

He acknowledged an increase in violence outside Baghdad even as the death toll is down in the capital but said the security crackdown was providing an example of how to fight it.

"The fact that the violence decreased in Baghdad, the terrorists went to the surrounding areas and these areas are breeding grounds for violence ... tribal leaders are carrying operations against them," he said. "The terrorist elements are backed into a corner and we are going to continue to carry out these operations."

U.S. military spokesman Rear Adm. Mark Fox also expressed confidence in the security sweep, saying half of the U.S. troop reinforcements are in place, but he warned it would not be easy to pacify the capital and asked for patience.

"The effort to exert security in Iraq will take time," Fox said at a joint news conference with al-Moussawi. "Our job will not be accomplished within days or weeks."

"We are going to see more violence in the coming weeks and months," he added.

More than 600 Iraqis were killed in sectarian violence last week alone, most in a series of high-profile suicide bombings. Among them were at least 152 people killed in a suicide truck bombing in Tal Afar -- the deadliest single strike since the war started four years ago. That bombing was followed by a shooting rampage against Sunnis that left at least 45 people dead.

Underscoring security concerns, Fox said two suicide vests were found unexploded Saturday in the heavily fortified Green Zone in Baghdad, less than a week after a rocket attack killed two Americans in the vast central area. Fox said the matter was under investigation, and al-Moussawi declined to comment on where the vests were found.

In other violence Sunday, two top Sunni officials escaped an assassination attempt in one Baghdad's most restive neighborhoods.

Omar Abdul-Sattar of the National Accordance Front, the biggest Sunni parliamentary block with 44 seats, and Omar al-Jubouri, an aide to Sunni Vice President Tariq al-Hashemi, were targeted by a roadside bomb when their convoy was passing through Yarmouk in western Baghdad, police said. Nobody was killed in the attack, but it came amid a recent rise in violence by suspected Sunni insurgents against members of the minority Islamic sect who are affiliated with the political process.

Separately, Kurdish lawmakers struck back against criticism over the Iraqi government's decision to endorse plans to relocate thousands of Arabs who were moved to the northern city of Kirkuk as part of Saddam Hussein's campaign to force ethnic Kurds out of the oil-rich city, in an effort to undo one of the former dictator's most enduring and hated policies.

The contentious decision on Kirkuk was confirmed Saturday by Iraq's Sunni Justice Minister Hashim al-Shebli on Saturday as he told The Associated Press he was resigning. Almost immediately, opposition politicians said they feared it would harden the violent divisions among Iraq's fractious ethnic and religious groups and possibly lead to an Iraq divided among Kurds, Sunni Arabs and Shiites.

The plan was virtually certain to anger neighboring Turkey, which fears a northward migration of Iraqi Kurds -- and an exodus of Sunni Arabs -- will inflame its own restive Kurdish minority.

The Kurds warned that derailing the decision, which could pave the way for a referendum on the city's fate as required by the constitution, "will put Iraq's unity at risk."

"Those who are putting sticks in the wheel of the political process are those who are calling for derailing this article," Saad al-Barzanchi, a Kudish lawmaker with Kurdish parliamentary block that holds 53 seats. "This is not a negotiable matter. To those who want to derail it ... we say: This is an alarm bell and threatens Iraq's unity."