Paris (AFP) - The affair reads like something out of a John Le Carre novel: two former French secret service agents accused of plotting to assassinate a senior opposition figure from a former African colony.

But General Ferdinand Mbaou, the target of the alleged plot over which the Frenchmen were arrested last month, says he is "not surprised".

Like several France-based opponents of Republic of Congo's President Denis Sassou Nguesso, Mbaou believes he has been targeted for criticising one of Africa's longest-serving leaders from what he believed to be a safe distance.

The 62-year-old general is known for his outspoken attacks on Sassou Nguesso, who has ruled the oil-rich central African country of 4.5 million people for nearly 35 years in total.

Mbaou fled Congo after his former boss, the country's first democratically-elected president Pascal Lissouba, was overthrown by Sassou Nguesso in 1997.

He had already survived an attempt on his life.

Mbaou believes it was the regime that sent hitmen to shoot him in the back as he was leaving his home in Bessancourt north of Paris in November 2015.

The greying 62-year-old still has the bullet lodged in his torso.

"The doctors couldn't remove it because it is in a tricky spot, close to the heart," he told AFP.

No one was ever charged over the 2015 attack, and little is also known about the latest alleged murder plot.

The interior ministry has declined to comment on the most recent affair, over which two former members of the DGSE intelligence agency have been charged with a criminal conspiracy and possession of explosives.

Congolese opposition members based in France say it fits a pattern of intimidation and harassment.

Roland Levy Nitou, head of a group called The Outraged of 242, after Congo's international dialling code, told AFP threats were a part of his "daily life".

"They told me on the phone: 'One day we'll get you'," said the 42-year-old logistics worker, adding that his parents were in hiding in Congo after they too received threats.

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- 'Ill-gotten gains' -

Nitou believes his group is in the president's sights for posting videos on the internet of around a hundred luxury properties where Sassou Nguesso, his family and some of his ministers allegedly live it up when in France.

Some of the properties have been targeted by a landmark French investigation into the purported ill-gotten gains of three big-spending African "first families" -- those of the Republic of Congo, Equatorial Guinea and Gabon.

Nitou's video of a palatial villa in the Mediterranean resort city of Nice -- which he claimed belonged to Sassou's family -- has racked up nearly 9,000 views on YouTube.

Nitou believes the videos have hit a nerve in a country where around one-third of the population lived on less than $1.90 (1.63 euros) a day in 2016, according to the World Bank, despite Congo sitting on large oil reserves.

In May, as he was on his way to a demonstration against Sassou Nguesso, he was beaten up by one of the president's supporters.

No one has been charged over the case.

Nitou accuses France of "protecting Sassou Nguesso" -- a claim to which the French foreign ministry declined to respond.

Paris has a long history of backing authoritarian pro-French regimes in former African colonies.

But President Emmanuel Macron, like his Socialist predecessor Francois Hollande, has vowed an end to meddling in African affairs.

The Congolese government, for its part, denies going after opponents beyond its borders.

"All those opposition members who accuse Congo over things that happen in France are wrong," said a government source in the capital Brazzaville.

The source claimed Mbaou "lived freely in Congo between 2009 and 2012" -- although he was in fact jailed twice in Brazzaville during that time.

"Why would we take the risk of making an attempt on his life in France?" the source asked.

- Third-term turmoil -

Congo was plunged into turmoil in 2015 when Sassou Nguesso called a referendum on changing the constitution to allow him to seek a third successive term in office.

Hollande expressed support for the referendum -- a move seen by Congo's opposition as a betrayal of his promise not to meddle, and a tacit statement of support for the incumbent.

The opposition boycotted the vote and also cried foul a year later when Sassou Nguesso won another five years in power.

In its 2017/2018 report on the country Amnesty International said "dozens" of Sassou Nguesso's opponents were still in detention.

They include former presidential candidate General Jean-Marie Michel Mokoko who was sentenced to 20 years behind bars in May on charges of "undermining state security" for urging protests after Sassou Nguesso's re-election.

Another opposition leader, Paulin Makaya, was released recently after almost three years in prison but has been prevented from leaving the country.