The authorities in the Democratic Republic of Congo are seeking to lift former President Joseph Kabila's immunity from prosecution after accusing him of backing rebels in the east.

There was a "substantial body of documents, testimony and material facts" linking Kabila to the M23 armed group, Justice Minister Constant Mutamba said on Wednesday.

The M23 currently controls parts of the mineral-rich east of the country after making significant advances earlier this year.

Kabila, 53, has not commented on the accusations but has in the past denied any connection with the insurgents.

He led DR Congo for 18 years, after succeeding his father Laurent, who was shot dead in 2001. Joseph Kabila was just 29 at the time.

After stepping down, he was given the title of "senator for life", which gives him legal immunity.

In order to pursue a legal case, DR Congo's military prosecutor has asked the senate to overturn this.

Kabila has been living outside the country, in South Africa, for the past two years. But at the beginning of last month he said he would be returning to help find a solution to the conflict in the east.

A few weeks later, there were reports that the former president had come back and was in Goma, one of the cities captured by the M23.

But these were denied by his political party, the People's Party for Reconstruction and Democracy (PPRD).

Last month, the authorities banned the PPRD because of its "ambiguous attitude" to the occupation of Congolese territory by the M23.

Justice Minister Mutamba, who last month ordered the seizure of Kabila's assets, said the former president should return to the country and "face justice... and present his defence".

DR Congo and Rwanda, which denies accusations it backs the M23, may be edging towards a peace deal to end the fighting, which has seen hundreds of thousands of civilians forced from their homes in recent months.

The two countries signed a preliminary agreement in Washington last week and said they would have a draft deal by Friday.

After being sworn in as president following his father's death, Kabila twice won elections. His second and final elected term in office officially ended in December 2016, but he refused to step down, saying it wasn't possible to organise elections, leading to deadly protests.

He stayed in power for two more years until elections were finally held in 2018.

In January 2019, he handed power to Félix Tshisekedi, the official winner of a disputed election, which many election observers said was rightfully won by Martin Fayulu.

He accused Kabila and Tshisekedi of agreeing a deal to exclude him from power - something both men have denied.

But relations between the pair worsened and their parties' coalition was formally ended in December 2020.

Kabila left DR Congo in 2023, officially to study in South Africa.

In January 2024, his doctoral thesis on the geopolitics of African relations with the US, China and Russia was validated at the University of Johannesburg.

Additional reporting by Aaron Akinyemi and BBC Monitoring