Iraq's parliament has voted to back Prime Minister Nouri Maliki's new drive to improve security in Baghdad.
Nouri Maliki said no armed groups would be spared
Mr Maliki said operations would be under Iraqi control with US troops acting in support.
The key bloc of MPs allied to radical Shia cleric Moqtada Sadr - which had boycotted parliament for two months - gave its backing to the plan.
The vote came as a massive car bomb killed at least 26 people in the Karrada shopping district of Baghdad.
The attack came shortly after two mortar attacks on the heavily fortified Green Zone, home to the US embassy and Iraqi government buildings.
Earlier, at least five people were killed in two bomb attacks.
'All armed groups'
The Mehdi army militia loyal to Mr Sadr is to be a focus of the security drive.
Mr Maliki said he wanted to disarm all groups - including militias, insurgents and criminals - leaving weapons only in the hands of government forces.
"All those who break the law will be hunted down," he said.
The BBC's Mike Wooldridge in Baghdad says it is significant that Mr Sadr's political bloc supported the plan.
The group offers key support to Mr Maliki in parliament.
It had boycotted parliament in November to protest against a meeting between Mr Maliki and US President George W Bush.
Mr Maliki promised security forces would take on all armed groups regardless of religious or political affiliation.
The prime minister has been accused of not doing enough to crack down on the Mehdi army but on Tuesday the military announced that 600 Mehdi army fighters had been arrested.
Mr Maliki said even the headquarters of political parties could be raided "if they are turned into a launch pad for terrorism".
"There will be no safe haven - no school, no home, no (Sunni) mosque or Shia mosque," he added.
Under the joint US-Iraqi plan, about 50,000 Iraqi soldiers and police backed by more than 30,000 US troops will go through Baghdad district by district, attempting to drive out armed groups.
The Iraqi army is to be in charge of the new security drive
An advance guard of 3,200 troops arrived in Baghdad on Sunday, part of President Bush's plan to send an extra 21,500 troops to Iraq - most of them earmarked for operations in the capital.
The Iraqi defence ministry said 30 suspected militants were killed on Wednesday as US and Iraqi forces fought a fierce battle with insurgents in the Sunni-dominated Haifa Street.
Much of the city has become increasingly dominated by militias which have turned whole neighbourhoods into sectarian enclaves.
Mr Maliki promised that squatters would be cleared from homes they are occupying to allow the return of refugees.
Tens of thousands of people have fled their homes in Baghdad and the UN says nearly 500,000 people are internally displaced within Iraq.