Iraqi army vehicles moving toward Diwaniyah, south of Baghdad, after gunbattle between Iraqi forces and militiamen of the Mahdi Army

Iraqi officials say at least 40 Shi'ite militiamen and 20 Iraqi soldiers have been killed in an eruption of fighting in the southern part of the country. A U.S. military official in Baghdad says local police called in the Iraqi army and, together, repelled the insurgents.

The fighting began late Sunday in the Shi'ite-majority city of Diwaniyah, about 130 kilometers south of Baghdad.

Officials say the fighting broke out as Iraqi security forces were carrying out raids to collect illegal weapons from Mahdi Army militiamen.

U.S. Army Brigadier General Dana Pittard, in a briefing from Baghdad for reporters at the Pentagon, says Iraqi security forces were able to defeat the attackers.

"The Eighth Iraqi Army, working closely with Iraqi police, repelled the attacks of the insurgents down there in Diwaniyah," said General Pittard. "There was some tough fighting that went on, but I think the Iraqi Army did very well."

The Mahdi Army group is loyal to the radical Shi'ite cleric, Muqtada al-Sadr, whose movement holds seats in the Iraqi parliament, as well as Cabinet posts.

General Pittard says there was good cooperation between Iraqi security forces.

"If there is something that the Iraqi police cannot handle, then they will call either the national police or the Iraqi army, and we saw that as an example in Diwaniyah," he said. "We had a situation, that, at least initially, was beyond the capability of the Iraqi police. So, they called in the Iraqi army. The army and the Iraqi police together, as a force, repelled the insurgents. I think that is a good news story."

Also Monday, a suicide bomber blew himself up outside the Interior Ministry in Baghdad, killing at least 16 people and wounding dozens.

Violence on Sunday killed more than 60 Iraqis, and eight U.S. soldiers died in several attacks.

Despite the upsurge in violence over the past two days, U.S. military officials say stepped up U.S. and Iraqi patrols in Baghdad have reduced violence in the capital.

That security operation was ordered by Iraq's new prime minister after a spike in sectarian violence left thousands of people dead in the worst bloodshed since the U.S.-led invasion in 2003.