Chad's newly elected President Mahamat Idriss Deby was sworn in to succeed his late father on Thursday, after three years as an interim leader under military rule in the central African country.

Deby seized power after rebels killed his father, long-standing President Idriss Deby, as he was visiting troops fighting militias in the north of the country in 2021.

The older Deby had ruled Chad - which is rich in oil resources but one of the poorest countries in Africa - since a coup in the early 1990s.

Chad was the first of six junta-led states in West and Central Africa to hold elections following a string of coups over the past four years that further destabilised a volatile region.

Even so, Mahamat Idriss Deby's victory this month was controversial. He won a sweeping 61% of votes in the tense May 6 poll that two losing candidates, including runner-up Succes Masra, unsuccessfully challenged on allegations of fraud.

Masra, who was Deby's prime minister, came second with 18.54% of votes. He resigned on Wednesday after results were confirmed last week.

Before the election, some opposition parties and civil society groups had called for a boycott, saying Deby and his allies and clan control the main institutions of power.

"To my brothers and sisters who did not choose me... I would like to say that I respect your choice, which contributes to the vitality of our democracy," Deby said after taking the oath of office. He promised that 70% of the government's budget would be spent on social welfare.

More than 40% of Chad's population live below the poverty line, and extreme poverty has increased in past years according to the World Bank.

The arrival of over half a million war refugees from neighbouring Sudan after civil war erupted there in April 2023 has added to the pressure on the Chad's resources.

Hundreds of people were gathered outside the Palace of Arts and Culture in the capital N'Djamena before the swearing-in ceremony began.

Several African leaders attended the event, including the current African Union Chairperson, Mauritania's President Mohamed Ould Cheikh AI- Ghazouani, Gabon's junta leader Brice Oligui Nguema, and the interim prime minister of Niger, which has been under military rule since a coup last year.