Police in Switzerland and France carried out a number of co-ordinated raids on properties linked to one of the world's richest men as part of a global investigation into allegations of corruption surrounding a multibillion dollar mining deal.

Officers in Geneva raided the offices of a firm that provides management services for BSGR, a company controlled by Israeli billionaire Beny Steinmetz, while in France police raided the home of a director of the management services firm. Up to 20 police raided the offices of Onyx Financial Advisors, according to a security guard quoted by Reuters, and took away a number of documents. The Guardian understands that the raids were mounted at the request of the US department of justice, which has spent more than six months investigating BSGR's acquisition of lucrative mining concessions in the former French colony of Guinea [see footnote].

Steinmetz, 57, secured the rights to extract half the ore at Simandou after investing $165m in exploration, and then sold half his stake to a Brazilian mining corporation for $2.5bn.

In a country where millions of people live in desperate poverty, without running water, electricity or a functioning infrastructure – while sitting on some of the richest mineral deposits in the world, it was a deal that caused widespread anger and resentment.

Shortly after FBI agents began investigating the circumstances surrounding the Simandou deal to establish whether there had been any breach of the US Foreign Corrupt Practices Act and anti money-laundering laws, an associate of Steinmetz was arrested in Florida.

The FBI had covertly recorded a series of meetings during which the man had allegedly attempted to secure the destruction of documents detailing the way in which the iron ore concession was acquired. He has been charged with attempting to pervert the course of justice and is due to stand trial later in the year. He denies any wrongdoing.

Following the raids in Switzerland and France a spokesman for Onyx said: "Onyx has absolutely nothing to hide. We are co-operating fully with the authorities but are unable to comment further at this time."

The company's chief executive, Dag Cramer, added that the firm had "provided the Swiss authorities with information".

Steinmetz and BSGR deny any wrongdoing over the Simandou deal and say they are the victims of a smear campaign that is being led by the current president of Guinea, Alpha Condé, in an attempt to divert attention from his domestic political problems. Condé, who denies this, is conducting a parallel investigation to that being conducted by the FBI, examining a number of mining deals struck by past governments.

Last month the Guardian reported that Steinmetz was under investigation by the FBI as part of its corruption probe. While researching that article questions put to Steinmetz's spokesman Ian Middleton at the London PR firm Powerscourt twice resulted in threats of libel action from his lawyers at Mishcon de Reya.

Earlier this month Powerscourt also attempted to play down connections between Steinmetz's firm BSGR and Onyx, saying they were "separate and fully independent" of each other. Onyx was originally incorporated as BSG Management Services; the two firms share a number of directors as well as offices in London's Mayfair; and BSGR's website offers Onyx as a point of contact for anyone wishing to invest in BSGR.

Asked whether BSGR and Steinmetz had any comment on the raids in Switzerland and France, Middleton replied: "No they don't."

• This footnote was added on 4 September 2013. The Guardian understands that, in addition to being requested by the US department of justice, the raids were also conducted pursuant to a formal request from the government of Guinea.