Some of former French President Nicolas Sarkozy's top aides have been named in a scandal surrounding helicopter sales, allegations of kickbacks, and pressures on the Belgian Senate.

According to sources at French newspaper Le Monde, French courts have been probing since spring 2012 allegations of money laundering and corruption from the sale of 45 helicopters to Kazakhstan in 2010, during Sarkozy's time as president.

These contracts, worth an estimated grand total of 2 billion euros, may have been entered into with the government of Kazakhstan. In exchange for these contracts, it is alleged that the French president intervened within the Belgian parliamentary sphere to drop legal charges against three Kazakh businessmen residing in Belgium.

The transaction could be linked back to bribes, which were allegedly paid out to Sarkozy's former advisers, former Prefect Jean-François Etienne des Rosaies.

The probe was sparked by the transfer of suspicious funds into the account of Rosaies by his attorney. The kickback money may have been filtered through this attorney.

Jean-Vincent Brisset, a general in the French air force and a research director at the Institute for International and Strategic Relations (Institut de Relations Internationales et Stratégiques or IRIS) told VICE News that this practice is widespread.

"Retro-commissioning is a procedure that has been widely and legally practiced in the past," he said. "It's a classic mechanism that is found across all big business markets."

A retro-commission, more commonly known as a kickback, is the name given to an illegal financial transaction wherein a buyer, a seller, and an intermediary agree to inflate the commission amount. The surplus is then fed into a network of bribes. The term "retro-commission" was popularized by another scandal implicating Sarkozy — the "Karachi affair," which was comprised of a series of contracts, alleged to have illegally financed former French presidential candidate Edouard Balladur's campaign, in 1995.

As for the circumstances surrounding Sarkozy's state visit to Kazakhstan in 2009, and the first alleged mention of the contracts, according to sources at Le Monde, Brisset gave the following explanation: "When he's abroad, the president is trying to sell France. All presidents do this."

Olivier Maingain, president of the Francophone Democratic Federalists, and a deputy in the Belgian parliament, told VICE News that this will raise eyebrows in Belgium.

"The only witness account we have is the one given by Belgian Senator Armand De Decker, who claims he met with Jean-François Etienne des Rosaies in a Belgian seaside resort […] Following an article that appeared in French newspaper Le Canard Enchaîné, I requested on October 18, 2012 that a parliamentary commission be formed to investigate the matter," he said. "At the time, the commission was not instituted due to a lack of support. But the re-emergence of this case in France will undoubtedly lead to questioning in Belgium."

The aforementioned article, published on October 3, 2012, suggested Rosaies had acted as intermediary between the French presidency and Decker, vice-president of the Belgium Senate, who may in turn have sped up the voting in of a law in favor of the three Kazakh businessmen.

Claude Guéant, then Chief of Staff at the Elysée, spoke on French radio station France Info on Thursday morning, declaring, "Neither Nicolas Sarkozy […] nor anyone in the Elysée took part in the negotiation of these business contracts. What I notice is that the day after the announcement on France 2 of Nicolas Sarkozy's candidacy to the presidency of the UMP, we have witnessed a frenzy of violations of judicial confidentiality."

The former French president — defeated in the last election by current President François Hollande — announced his political comeback in mid-September by putting himself forward as a candidate in his party's primary election, with a view towards the 2017 French presidency.

Sarkozy's name is linked to a dozen cases that are still under investigation, including the aforementioned Karachi affair, which unfolded against the backdrop of arms contracts involving Saudi Arabia and Pakistan in 1994, and a suicide mission that had killed 11 French nationals and 3 Pakistani nationals in 2002.

Virgile Dall'Armellina contributed to this article.