More than 1,100 Iraqi and US troops have carried out an operation in Baghdad's Shia stronghold of Sadr City, the US military has said.
More US troops are being sent to improve Baghdad's security
It said no weapons cache had been found or suspected militant arrested.
Meanwhile five people were detained in an early-morning raid by UK and Iraqi troops in the southern city of Basra.
The raids came as Iraqi PM Nouri Maliki said he was offering an olive branch to insurgents who accepted the language of reconciliation and dialogue.
Those who did not would fall foul of a security crackdown which would "cover every inch of Iraq", he said.
Mr Maliki has said he will reshuffle his cabinet within the next two weeks.
No details have been given, but reports quote unnamed officials as saying he is expected to dismiss all six ministers loyal to the Shia cleric, Moqtada Sadr, who has been criticised by the United States.
Mr Maliki said political consensus could only be achieved in Iraq once the country was stable.
"We do not need to implement security measures except against those who reject the language of reconciliation and dialogue, those who insist on restoring the past," he said.
"We present in our hand a green olive branch, and in the other hand we present the law ... Operation Imposing Law started in Baghdad, it will cover every inch of Iraq."
He did not specify whether insurgents who stopped fighting would be given an amnesty.
Shortly after Mr Maliki's announcement, 600 US troops and 550 Iraqi soldiers entered Sadr City, as they continued to implement a major new security plan.
The US has repeatedly said that one of the keys to improving security in Iraq is to tackle Shia militias, such as the Mehdi Army, controlled by Mr Sadr.
US military spokesman Scott Bleichwehl said residents were co-operative and there was no incident during the operation.
In Basra, five people were held by British and Iraqi forces on suspicion of involvement in roadside bomb attacks against the multinational forces and Iraqi civilians, as well as kidnaps, torture and murder.
As a result of information obtained, Iraqi counter-intelligence forces then raided the National Iraqi Intelligence Agency headquarters, where "further evidence of significant criminal activity such as torture" was found and a number of prisoners released.
The BBC's Jim Muir in Baghdad says the agency is not the first to be involved in allegations of torture by Shia militias.
Meanwhile the US military announced the death of three more servicemen in Anbar province.
A marine was killed on Saturday. Another marine and a sailor died on Friday.