Iraqi officials say at least 40 Shi'ite militiamen and 20 Iraqi soldiers have been killed in fierce fighting in the southern part of the country.

The fighting began late Sunday in the Shi'ite majority city of Diwaniyah. Authorities say Iraqi security forces carried out raids aimed at collecting illegal weapons from militiamen of the Mahdi Army.

The Mahdi Army fighters are loyal to radical Shi'ite cleric Muqtada al-Sadr, who leads a faction of the Iraqi government. Prime Minister Nouri al-Maliki has vowed to disband militias as part of his national reconciliation plan.

Earlier Monday, a suicide car bomber blew himself up outside the Interior Ministry in Baghdad, killing 16 people and wounding more than 40.

Despite a spike in violence over the past two days, a U.S. military spokesman said a security operation in Baghdad has reduced violence in the capital.

Violence in the southern city of Basra, the northern city of Kirkuk and other parts of Iraq on Sunday killed more than 60 people.

The U.S. military in Iraq says eight American soldiers also were killed Sunday in several attacks.

In another development, British Defense Minister Des Browne met with his Iraqi counterpart, Abdul-Qader Mohammed Jassim al-Mifarji, in Baghdad.

Browne was expected to discuss plans for British troops to hand over security duties in southern Iraq to Iraqi troops.