The US-appointed Iraqi Governing Council has announced the formal establishment of a war crimes tribunal.
Saddam Hussein could be tried in absentia
The court will prosecute officials of Saddam Hussein's regime - and could try the ousted leader himself in absentia.
Iraqi judges will preside over the tribunal, with international legal experts acting only as advisers, coalition authorities say.
Human rights groups have expressed reservations, saying Iraqi judges are not sufficiently capable.
Among cases that could be investigated are:
The reported killing of 8,000 members of the Kurdish Barzani clan in 1983
- The use of chemical weapons on 16 March 1988 against Kurds in the city of Halabja, which left 5,000 dead and 7,000 injured or with long-term illnesses
- The reported killing of 300,000 Shia Muslims after the 1991 Gulf War
IGC in charge
The IGC reportedly voted to create the court on Tuesday, but the formal announcement was delayed until Wednesday.
"Today is an important historic event in the history of Iraq," current IGC President Abdel-Aziz al-Hakim said.
MASS GRAVES IN IRAQ
Kirkuk: Kurdish officials report discovery of 2,000 bodies
Muhammad Sakran: Reports say more than 1,000 bodies found
Babylon: Children's bones reportedly among remains found
Al-Mahawil: Up to 15,000 bodies feared buried
Najaf: 72 bodies found
Basra: Grave believed to contain about 150 Shia Muslims
Abul Khasib: 40 bodies reportedly found
Mr Hakim said the tribunal will cover crimes committed from 14 July 1968 - the day Saddam Hussein's Baath Party came to power - until 1 May 2003 when US President George W Bush declared major hostilities over.
Since then, more than 200 mass graves have been unearthed across the country - and about 5,500 people have been arrested , even though it is not known how many of those are war crimes suspects.
Some of the 55 Iraqis who are on Washington's so-called most wanted list are expected to be among the first to be tried.
Thirty-eight people on the list have been captured.
They could face charges of crimes against humanity, war crimes and genocide.
Among other former top Iraqis who could face the tribunal is Tariq Aziz, the former Deputy Prime Minister, and
Ali Hassan al-Majid, known as Chemical Ali, for his alleged role in the chemical attacks against the Kurds.
'Chemical Ali' - number five on the US list of most wanted Iraqis
Saddam Hussein himself remains at large.
It is unclear when the first cases will be heard.
All the trials will be held in Iraq.
The IGC has made no decision on imposing the death penalty, Mr Hakim said.
One IGC member said the proceedings would be open to the public - and could be broadcast on television.