The Blackwater guards were employed to protect US personnel in Iraq
Iraq has begun collecting signatures for a class action lawsuit on behalf of people killed or wounded in incidents involving US security firm Blackwater.
It will seek compensation for a number of such cases, the office of Prime Minister Nouri al-Maliki said.
Incidents include the 2007 killing of 17 Iraqis in Baghdad's Nisoor Square.
Last month, a US judge dismissed charges against five Blackwater guards over those killings, which Iraqi officials described as "regrettable".
Immediately after the US decision, the Iraqi government issued several angry statements pledging that it would continue to "act forcefully and decisively to prosecute".
It has become a notorious incident in Iraq, with the government now taking the initiative in organising the families of the victims to launch civil suits against Blackwater, says the BBC's Jim Muir in Baghdad.
THE BLACKWATER INCIDENT
16 Sep 2007 - 17 Iraqi civilians killed in Nisoor Square, Baghdad
Iraq said - civilians fired on by Blackwater guards without provocation
Blackwater said - Iraqis killed in shoot-out when Blackwater convoy ambushed
Iraqi eyewitnesses - guards fired on white sedan that failed to slow down and then fired into surrounding area as people tried to flee
Nov 2007 - New York Times quotes FBI officials saying killings of at least 14 of the Iraqis were "unjustified"
Dec 2008 - five guards charged with 14 counts of manslaughter
About 50 family members turned up at the prime minister's office after being invited to a meeting at which most of them signed powers of attorney, authorising the government's lawyers to sue the company on their behalf.
Some confirmed that they had already signed compensation agreements with Blackwater. Others said they had neither signed anything nor taken any compensation. They included a man whose son was killed in the Nisoor Square incident.
Lawyers for the five guards say they were acting in self-defence, but witnesses and family members of those killed maintain that the shooting on 16 September 2007 was unprovoked.
Investigations have produced no evidence to support the guards' claim, our correspondent says.
The incident caused widespread public anger against foreign security companies operating in Iraq, and their activities have been severely curbed since then.