More than 3,000 US and Iraqi troops have launched a major offensive on a rebel stronghold south of the capital, Baghdad, the US Central Command says.
Its press release said more than 30 suspected insurgents were seized in the sweep in the Babil province.
It said the forces seized a suspected rebel training camp and secured a key bridge across the Euphrates River often used by insurgents.
No casualties have so far been reported among the assault force.
The operation in the Babil region - which centres on the town of Hilla - follows a US-led blitz at the weekend on another rebel stronghold, Samarra, to the north of Baghdad.
Dozens of people, including a number of civilians, were killed in the two-day operation.
Experts say the US-led Multinational Forces and Iraq's interim government may be tempted to build on the successful Samarra operation to secure other areas where rebels have been active, in time for scheduled elections in January.
"Iraqi and multinational forces today kicked off their most sweeping operation to date in northern Babil, moving against
multiple targets across the central Iraqi province in a continuing campaign to restore security and stability here," the press release said.
It said the offensive's main mission was "to assist Iraqi authorities in fostering security and stability for the nearly 900,000 citizens of the province".
The US Central Command said the Jurf Kas Sukr Bridge was believed to be a favoured corridor for insurgents moving into and out of key cities, including Baghdad and the rebel stronghold of Falluja.
The operation was led by the US 24th Marine Expeditionary Unit, the press release said.
It said that more than 160 suspected rebels have been captured in co-ordinated US-Iraqi operations in the Babil province since July.