Iraqi and US troops fanned out across Baghdad on Wednesday as part of a long-awaited security plan to curb chronic bloodshed, but seven people died elsewhere in a US helicopter crash.
It was the fifth US chopper lost in less than three weeks, although there was no immediate word on whether enemy fire had brought it down like the other four aircraft.
US military spokesman Major General William Caldwell said that implementation of the Baghdad stabilisation plan unveiled by President George W Bush last month was now fully under way.
"The plan is being fully implemented as we speak," he told reporters.
Caldwell emphasised that Iraqi commander Lieutenant General Abboud Qanbar "is in charge" of the operation, eventually expected to involve some 80,000 Iraqi and US troops.
US Major General Kenneth Hunzeker, who oversees training of Iraqi police, said each of Baghdad's nine police districts would host an Iraqi army brigade of 5,000 or so men, along with Iraqi police forces and a US battalion of between 300 and 500 troops.
The police stations would integrate with or be supplemented by joint security stations manned around the clock by Iraqi-US units, Caldwell said.