Prime Minister Nouri al-Maliki launched the crackdowns to extend the authority of the government over areas in Baghdad and elsewhere that largely have been under the control of armed groups since the U.S.-led invasion in 2003.

"They were intending to besiege Baghdad and control it," Maliki said. "But thanks to the will of the tribes, security forces, army and all Iraqis, we defeated them."

He was speaking at ceremonies marking the fifth anniversary of the 2003 assassination of Ayatollah Mohammed Baqir al-Hakim, a leading opponent of Saddam Hussein who was killed in a truck bombing in the southern Iraqi city of Najaf after returning from exile in Iran.

Such attacks plagued Iraq after the U.S.-led invasion, but violence in the country has fallen to its lowest level in four years. The change has been driven by the 2007 buildup of U.S. forces, the Sunni tribal revolt against al-Qaeda in Iraq, and Maliki's crackdowns, among other factors.

"Under the national unity government, the Iraqis have achieved national feats . . . that are now lighting the course of our march," Maliki said.

Bolstered by this confidence, the prime minister plans to visit the United Arab Emirates today and also Italy and Germany later in the month - apparently hoping that improved security at home will pay dividends in greater international support.

Iraq is also enjoying a surge in oil revenue driven by record crude prices and the highest production levels since Hussein's ouster. The government expects to earn $70 billion from oil in 2008 if prices remain high.

Planning to put some of this money to work, the Iraqi government yesterday held a groundbreaking ceremony for a major project to refurbish the main road to the Baghdad airport. The road was once considered one of the most dangerous in the world but has become safer with the decline in violence in the country.

Despite recent gains, daily attacks continue throughout Iraq. Gunmen attacked a police patrol yesterday near Mosul, 225 miles northwest of Baghdad, killing one policeman, police said.

Also yesterday, one policeman was killed and a passerby was injured near Nasiriyah, 200 miles southeast of Baghdad, when a bomb attached to the policeman's car exploded, police said.

On Friday, one Iraqi citizen was killed and seven were wounded when an explosion occurred in the western Baghdad neighborhood of Yarmouk, the U.S. military said.