The International Criminal Court on Monday authorised an investigation into violence that left some 3,000 people dead after Ivory Coast's disputed presidential election last year.
The violence erupted after former President Laurent Gbagbo refused to cede power to opposition leader Alassane Ouattara after losing the election last November.
Ouattara finally took office in May and asked the international court to investigate crimes committed by both sides during the post-election crisis.
Ivory Coast's Justice Minister Jeannot Ahoussou Kouadio welcomed the decision.
"It's what we've wanted. It's what we've been asking for," he told The Associated Press by phone from Yamoussoukro. He said justice handed down through such a "strong and respected institution" would be the only way to ensure "total transparency."
Kouadio pledged there would be no impunity for pro-Ouattara fighters who were found by the court to have committed crimes during the crisis.
Gbagbo's spokesperson Kone Katinan said if he is to be judged, it should be by his own people rather than an international tribunal.
Gbagbo "remains deeply Pan-African and he is fighting for the sovereignty of the Ivorian people. He believes it is to this people that he must be held accountable, because it is from this people that he received his mandate (to govern)," Katinans said.
The announcement signaled the start of the court's seventh investigation, all of them in Africa. So far, none of the cases has reached a verdict.
Ivory Coast is not a member of the court, but has accepted its jurisdiction in the case. It is the first time the court has opened an investigation in a non-member nation following such a recognition of jurisdiction by a non-member state.
Prosecutor Luis Moreno-Ocampo said he would begin his investigation immediately.
"From today, the prosecution will collect evidence impartially and independently, and as soon as possible we will present our cases before the judges, who will ultimately decide who should face trial," Moreno-Ocampo said in a statement.
Monday's decision came less than a week after Ivory Coast's new government launched a South African-style Truth and Reconciliation Commission that aims to find peace in the aftermath of the violence.
Moreno-Ocampo said his investigation "should be part of national and international efforts to prevent future crimes" in Ivory Coast.
Judges approved Moreno-Ocampo's request to open an investigation into crimes committed since November 28, 2010. They also asked the prosecutor to send them within a month information on possible crimes committed in Ivory Coast between 2002 and 2010, signaling they may yet broaden the scope of the investigation to include earlier violence. The International Criminal Court can only investigate crimes committed since it came into existence in 2002.
Ivory Coast was once one of Africa's most prosperous nations but has been crippled by a decade of conflict which started with the 1999 coup, followed by flawed 2000 elections that first brought Gbagbo to power.
Serophin Kokri, a 32-year-old waiter in Abidjan, urged the court to widen the investigation.
"It's a good thing," he said of the new investigation. "It's going to elucidate what really happened. But they shouldn't just look into what happened since December. They should go back to 2002 to see how we ended up here. Before that, Ivorians didn't know guns."
Human Rights Watch said the election violence capped more than a decade of human rights violations that largely have gone unpunished.
"The investigation should cover crimes committed prior to the election for the ICC's involvement to have maximum impact," said Elise Keppler, a senior counsel for the group. Among those accused of abuses in earlier years were forces under Guillaume Soro, Ouattara's current prime minister, the New York-based group said.
Although domestic courts have begun prosecuting postelection crimes, "they appear glaringly one-sided," with charges filed against 118 Gbagbo supporters and none against Ouattara's allies, Human Right Watch said.
Gbagbo failed to hold elections when his first term was up in 2005. When another five years was up last November, he refused to accept his electoral defeat, setting off a five-month-long crisis that turned the once-chic commercial capital of Abidjan into a war zone.
Among its other cases, the court has filed arrest warrants for Sudanese President Omar al-Bashir and Libya's Moammar Gadhafi. The court has no police force to execute such warrants. Prosecutions are under way of accused warlords from five other countries.