The U.S. military in Iraq says troops killed 20 suspected terrorists during an operation against a network transporting weapons from Iran to Iraq.
U.S. military statement says six other suspected terrorists were wounded and one detained during the raids in Amarah and Majjar al-Kabir.
It says the terrorist network was also known to bring militants from Iraq to Iran for training.
In Nasiriyah, at least four people were killed and more than 50 wounded in clashes between Iraqi police and Mahdi Army fighters.
In Baghdad, Iraqi police say two car bombs killed at least seven people lining up to buy fuel, while a car bomb in Fallujah killed at least three people.
Sunday, the U.S. military commander in Iraq said hopeful signs, such as a drop in sectarian killings, have emerged since more American troops arrived in the country. But General David Petraeus said on Fox television that it could take up to a decade to completely stabilize Iraq.
Petraeus also says U.S. military officials have "real concerns" about conditions in some areas in and around Baghdad, where fighting continues between opposing Shi'ite and Sunni militias.
Some information for this report was provided by AP and Reuters.