A powerful top aide to DR Congo's President Felix Tshisekedi went on trial for corruption on Monday in a case without precedent in the vast African country.

Tshisekedi's chief of staff Vital Kamerhe, who has been at the very heart of political life in DR Congo for two decades, is accused of embezzling more than $50 million.

A grey-bearded Kamerhe, 61, appeared in a prison jumpsuit before a court set up within Kinshasa's central prison compound, where he has been in custody since April 8.

Two other defendants in the case, a Lebanese businessman and another presidential official, also appeared during the first hearing which was broadcast by the state channel RTNC.

Kamerhe's supporters charge that the case is politically motivated, a possible attempt to prevent him from running in the next presidential election in three years' time.

"Never in Congo's political history over the past two decades has such an important player on the political scene been put behind bars," New York University's Congo Study Group (CSG) said in an analysis.

The case against Kamerhe is part of a broad investigation that is supposed to mark the "renewal" of the Congolese justice system in the fight against corruption among the elite since the country's independence in 1960.

Kamerhe, once a pillar of the regime of former president Joseph Kabila, is the leader of the influential Union for the Congolese Nation and previously served as parliamentary speaker.

He emerged as Tshisekedi's main ally in his quest for power after Kamerhe himself bowed out of the presidential race in December 2018, the first peaceful power transfer in the history of the Democratic Republic of Congo.

- 100-day action plan -

Kamerhe, said to have been in charge of authorising public expenditure, is accused of embezzling public funds intended to finance major works under a "100-day" emergency action plan launched by Tshisekedi after he took office in January last year.

The defendants are accused of embezzling almost $49 million from funds for building 4,500 pre-fabricated homes for poor people and allegedly siphoned off another $2 million from a programme to build housing for police and the military in Kinshasa.

Kamerhe, who has not stood down or been sacked since being charged, has denied the allegations against him, saying all public sector contracts were "inherited" from previous governments.

Although Kamerhe's arrest is seen as a strong signal in the anti-graft fight, some remain sceptical, seeing the case as a possible settling of scores within the governing coalition.

MPs from Kamerhe's party have denounced the "arbitrary arrest" and "humiliation" suffered by their leader while on social media, his supporters say it is a bid to remove him from the 2023 presidential race despite a deal with Tshisekedi.

Kamerhe's lawyers said on Monday that they had filed an application for temporary release, after another request was denied last month.

The trial was initially expected to be held in Kinshasa's high court but was later moved to the prison complex where Kamerhe has been held for more than a month.

Defendants, judges and lawyers wore masks during the hearing, as the official toll of coronavirus cases in the country passed the 1,000-mark, including 41 deaths, with a major outbreak at a prison in the capital.

The session was briefly suspended after Kamerhe's co-defendant, 79-year-old Lebanese businessman Samih Jammal, appeared to be fainting in his wheelchair as he breathlessly confirmed his identity to the court.

The biggest country in sub-Saharan Africa, the Democratic Republic of Congo has an abundance of natural resources, but most of its 80 million people live below the threshold of poverty.

The country struggles with a long history of conflict, poor governance and graft.

Kamerhe served as president of the National Assembly from 2006 to 2009 but moved to the opposition ranks in 2011, running in elections that year.

He initially stood in the 2018 presidential poll but bowed out to team up with Tshisekedi.

The two leaders signed a political agreement in Nairobi in November 2018 that gave birth to a joint platform, Heading for Change, and which allowed Kamerhe to run for president in 2023.

Kamerhe's UNC has 16 seats in parliament and several ministers in Tshisekedi's huge coalition government.