Paris - Former British mercenary Simon Mann, who led a failed 2004 coup in Equatorial Guinea, has accused US billionaire George Soros of plotting to overthrow its president, in testimony at a high-profile trial in Paris.He also accused William Bourdon, a lawyer for the anti-corruption NGO Transparency International, of being part of a plot to topple President Teodoro Obiang Nguema, Africa's longest serving leader after ruling his country with an iron fist for nearly four decades. Mann's remarks were made as he testified on behalf of the president's playboy son, Teodorin Obiang, who is currently on trial in Paris accused of plundering Equatorial Guinea's coffers to fund his jetset lifestyle in France. A former British special forces officer who was educated at the elite Eton College, Mann led the 2004 coup plot to overthrow Obiang but was arrested in Zimbabwe beforehand and jailed. In 2008, he was extradited to Equatorial Guinea, but released a year later after being pardoned by Obiang. Mann, 65, said he remained in contact with Obiang, telling the court that he had "warned" the president in 2011 that Soros and Bourdon were plotting to oust him. 'I warned the president' "I warned the president that ... George Soros, as well as Severino Moto and Ely Khalil, were intending to overthrow the government," he said, referring to exiled opposition leader Severo Moto Nsa and a Lebanese businessman.Both Moto and Khalil were involved in the attempted coup of 2004, which sought to install Moto as president of the oil-rich west African state.Mann said he could not "prove" his claim, saying: "I don't have written evidence.""I explained to the president it could be by any means," he said, saying the plotters had looked into all possible ways of ousting Obiang. "They were looking at all options, including legal."Asked if he had been paid to give his testimony in court, he said he had only been paid expenses. 'Extremely grave' AFP was not immediately available to reach Soros to comment on Mann's claims. But Bourdon - who is representing civil plaintiffs in the case against Obiang's son on behalf of Transparency International France - described Mann's allegations as "extremely grave", accusing him of "conduct which had plumbed the depths of filth."He asked that such claims be noted, saying he reserved the right to seek legal redress. Speaking outside the court, Mann claimed that the trial of Obiang was a sham whose real aim was to destabilise the regime in Equatorial Guinea. "Here is a criminal case setting out to go for a guy when in fact the motive is to destabilise and overthrow a recognised and legitimate regime," he said."I know that because Severo Moto Nsa and Ely Khalil were the two people who hired me to lead the 2004 attempted coup d'etat against the regime."Obiang's trial resumed in his absence on June 19 after a six-month delay pending his appeal to the International Court of Justice to scrap the proceedingsEquatorial Guinea questions France's right to put the president's son and current vice-president on trial, saying it violates his diplomatic immunity.The 48-year-old is suspected of using more than 100 million euros ($112 million) of state money to buy a six-storey mansion on Avenue Foch, one of the swankiest streets in Paris, as well as a collection of Italian supercars.Obiang, who once again did not appear in court, denies the charges, saying the money came from legitimate sources.