Inside two adjacent houses in an upscale area of Rwanda’s capital, the unfinished business of the country’s 1994 genocide unfolds. Members of the Genocide Fugitive Tracking Unit work from here to bring to trial dozens of key perpetrators who fled abroad after the killings, some of them to the United States — and 20 years later, there’s still no end in sight.

“In our lifetime we shall continue to pursue them, and those who come after us will continue to pursue them,” said Jean Bosco Mutangana, a Rwandan prosecutor who oversees the endeavor as head of the government’s international crimes unit. “You cannot have reconciliation without real, true justice being done.”

On Monday, Rwanda launched a week of official mourning to commemorate the 20th anniversary of the massacres in which more than 800,000 people, mostly ethnic Tutsis and moderate Hutus, died at the hands of Hutu extremists. The events, marked by displays of intense grief, began with a wreath-laying ceremony at the Kigali Genocide Memorial Center. Later, at Kigali’s main stadium, a flame was lighted that will burn for 100 days — the period covered by the killing sprees.

In the years since the genocide, this tiny East African nation has rebounded: Its economy is surging, poverty has declined, life expectancy has soared and it has been commended for its ongoing effort to achieve social reconciliation. But it has failed to bring to justice all those who led the massacres — a quest that has been likened here to the decades-long hunt for the Nazi leaders who planned and carried out the Holocaust. Many Rwandans note that an international tribunal created to judge the high-level killers known as génocidaires has delivered only 49 convictions, out of 95 indictments, since it began its work in 1995.

“Justice hasn’t been adequate, especially at the international level,” said Honoré Gatera, manager of the memorial center. “It’s been really a huge failure, mainly for the survivors’ community in Rwanda, to see that after 20 years there are still génocidaires around the world when the court is there for the last 19 years.”

The 1994 genocide in Rwanda claimed an estimated 800,000 lives in 100 days. Former Washington Post reporter Keith Richburg covered the conflict and looks back on the crisis two decades later. (Jason Aldag/The Washington Post)

Monday’s ceremonies were full of reminders of this perception that the international community has failed Rwanda. A French representative was noticeably absent after Rwandan President Paul Kagame accused France of involvement in the genocide in an interview with Jeune Afrique, a French-language magazine, last week. France, which was a close ally of the Hutu-led government that was in place before the genocide, in turn accused Kagame of distorting history.

In an address to visiting dignitaries and thousands of Rwandans, U.N. Secretary General Ban Ki-moon reiterated the United Nations’ remorse that its peacekeepers had failed to stop the genocide. “In Rwanda, troops were withdrawn when they were most needed,” Ban said.

A mixed record

The killings were triggered on April 7, 1994, when a plane carrying Rwanda’s Hutu president, Juvenal Habyarimana, and Burundi’s Hutu president, Cyprien Ntaryamira, was shot down near Kigali’s airport. Within hours, Hutu militias began targeting Tutsis with machetes, clubs and guns. They ordered the country’s Hutu majority via radio programs to exterminate the Tutsi “cockroaches.” Neighbors attacked neighbors. Teachers killed students. In mixed-ethnicity marriages, husbands handed over wives to be killed. Even churches were not sanctuaries, as several Catholic nuns and priests ordered killings.

Meanwhile, Western nations shied from intervention, as Bill Clinton, president at the time, acknowledged years later in a public apology for American inaction. On Monday, the U.S. delegation to the ceremonies was headed by U.N. Ambassador Samantha Power, who won a Pulitzer Prize for her book on U.S. failures to respond to genocides.

In the two decades since the massacres, Rwanda has drawn both praise and criticism. On the one hand, it can point to its record of economic and social progress. On the other, Kagame has been accused of ruling like a strongman and curbing freedoms. Opponents of the government have been jailed or assassinated, and the United States and other Western powers have slashed development aid over Rwanda’s backing of rebels in neighboring Congo, a charge Kagame has denied.

On the reconciliation of Hutus and Tutsis, the record is mixed. The government has outlawed any speech that creates ethnic tensions; citizens are now encouraged to not refer to themselves as Hutu or Tutsis, but as Rwandans, to emphasize national identity over tribe. Local tribunals known as gacaca — a meld of judicial court and truth and reconciliation commission — have overseen the release of many killers from jail after they confessed their crimes. Today, there are countless examples of offenders living peacefully next to the relatives of those they murdered.

Still, on a deeper level, tensions linger.

“We still have some barriers,” said Edouard Bamporiki, a poet and filmmaker who is also a member of Rwanda’s parliament. “Many Hutu families are still in the process of removing the shame. And there is pain and anger in the families of Tutsis. It’s not easy to forgive.”

Take Egide Nkuranga. His Hutu neighbors slaughtered his mother, elder brother, six nieces and many other relatives, mostly after U.N. peacekeepers left their area. Some of their killers returned a few years ago to his neighborhood after going through a gacaca court. But whenever he sees them, he avoids them. And they, too, walk away when they see him.

“I cannot sit down and share a Coke with my family’s killers,” said Nkuranga, 48, who is the vice president of Ibuka, a genocide survivors association that is seeking reparations from the United Nations. “Maybe it will happen, but not now.”

“Reconciliation for me comes after justice,” he added. “And we still need justice.”

Much left to be done

In a report late last month, Human Rights Watch declared efforts by the International Criminal Tribunal for Rwanda (ICTR) a relative success. The court has tried and convicted several senior figures who orchestrated the genocide, including former prime minister Jean Kambanda, former army chief of staff Gen. Augustin Bizimungu and former Defense Ministry chief of staff Col. Théoneste Bagosora.

Where the court has failed, the watchdog group said, is in relation to the Rwandan Patriotic Front, the mostly Tutsi rebel force led by Kagame that quelled the massacres. In doing so, rebels committed some crimes against humanity, the group noted, but not a single case has been prosecuted by the court.

As for the gacaca, where nearly 2 million low-level offenders were tried before the courts ended their work in 2012, Human Rights Watch described the system as having a “mixed legacy.” They were speedy, and attracted immense participation from Rwandans. But many of the trials were unfair, “marred by intimidation, corruption, and flawed decision-making, the group said.

Today, Rwanda remains determined to prosecute the genocide perpetrators still outside the country. The ICTR’s mandate ends at the end of the year, and Rwanda will be on its own in its quest to see full justice done.

In the past few years, the Genocide Fugitive Tracking Unit has issued arrest warrants for dozens of suspects living in Europe, Canada and the United States. Out of 11 suspects in the United States, three have been deported, according to Mutangana, the national prosecutor. In most cases, Western governments are reluctant to send suspects to Rwanda because they are concerned they won’t get a fair trial. And Rwanda has few extradition treaties with Western nations.

Most of the high-level figures behind the genocide who are still at large are thought to be in Africa. The one Rwanda wants most is Félicien Kabuga, a Hutu businessman alleged to have bankrolled the genocide. At one point, he was believed to be living in Kenya, enjoying the protection of senior leaders there.

Everyone in the fugitive tracking unit expects to be working two decades from now.

“The genocide remains fresh in the minds of Rwandans,” Mutangana said. “Trying these people here will send a message of justice being done and bring psychological healing to the survivors and to the country.

“Twenty years from now,” he predicted, “a big number of suspects will have been prosecuted. It will send the message of ‘never again.’ ”