Succes Masra, president of The Transformers party, had fled the country along with other opposition leaders several days after the bloody repression of demonstrations held on October 20 last year to protest military rule.
About 50 people, according to the government, or at least 300 according to the opposition and independent observers, were killed by police and military fire in the capital N'Djamena.
At least another 600 were rounded up and sent to an infamous remote desert jail where most were convicted and sentenced to prison in a mass trial, before being pardoned.
Masra returned to Chad on November 3 after he reached an agreement with the military, led by transitional president Mahamat Idriss Deby Itno.
The agreement included a "general amnesty" for those responsible for the killing of demonstrators on October 20, 2022.
Masra on Sunday called for calm amongst hundreds of his supporters gathered in N'Djamena, telling them not to "seek revenge," an AFP journalist reported.
He repeatedly emphasised a conciliatory message, saying he "prayed to God to soothe the hearts" of the victims and their families and "guide them towards collective responsibility."
"Reconciliation is not surrender," he said.
The rest of Chad's opposition, many of whose leaders remain in exile, have denounced the agreement reached between the government and Masra, calling it the latter's cozying up to power in the run-up to elections promised for 2024.
They are calling for a boycott of a referendum on a new constitution, which is scheduled for December 17 and due to set the stage for "free" elections and a return to civilian rule.
Max Kemkoye, president of the Union of Democrats for Development and Progress (UDP) party, said the rest of the opposition views the amnesty as a way of "shielding criminals from prosecution... who killed en masse, tortured, abducted and made young people disappear on October 20, 2022."
'We're on our feet'
Masra received multiple rounds of applause throughout his lengthy speech from supporters dressed in the national colors.
"His speech reassured the people, we're on our feet," said Etienne Josue, 25, an enthusiastic member of the crowd.
"After October 20, there was no hope," added 32-year-old Salim Abdoulaye, another attendee.
The opposition leader finished with a nod to future cooperation with the military leaders, calling President Deby "our brother."
"Deby can count on us as an ally of the people. We are ready to continue working with the authorities to find a comprehensive solution," he said.
Deby, a general, was proclaimed transitional president by the army on April 20, 2021 following the death of his father, Idriss Deby Itno, who had run Chad as a dictator for 30 years and was killed by rebels while visiting frontline troops.
Mahamat Deby had promised elections within 18 months, but after that date passed he put off a vote for another two years.
Chad Opposition Leader Calls for 'Reconciliation' with Military Government
FILE —Opposition leader Succes Masra (C) addresses the supporters of the Chadian opposition party Les Transformateurs for the first time since his return from exile in N’Djamena on November 19, 2023.
N'DJAMENA —One of Chad's main opposition leaders, recently returned from exile, on Sunday called for "reconciliation" with the military regime, a month before a constitutional referendum.