Steinmetz is cooperating fully with the Swiss authorities, his lawyer said in a statement.

According to the Bloomberg Billionaires Index, Steinmetz has a net worth of $7.4 billion, and his mining company BSG Resources owns a 49 per cent stake in the Simandou iron ore deposit in Guinea.

The government of Guinea has accused BSGR of paying bribes to obtain concessions under a previous government and is currently reviewing mining licenses including Simandou's.

BSGR denied the claims in a statement and said that the government of Guinea had not yet provided "any original evidence to support its false and malicious allegations against BSGR or Mr Steinmetz".

According to media reports, the Geneva home of Steinmetz was raided by police earlier this month.

The raid was ordered by Geneva's public prosecutor following a request by the government of Guinea.

Swiss police also raided the offices of Onyx Financial Advisors, which provides management services for BSGR.

BSGR said that the Swiss searches were in connection to the arrest of two BSGR employees who have been detained without charge for five months in the capital Conakry.

"In an attempt to justify their continued illegal detention, the government of Guinea has sent direct requests to the Swiss authorities to collect information on its behalf. The government of Guinea’s action are linked to its ongoing attempts to expropriate illegally mining rights belonging to BSGR at Simandou in south eastern Guinea," BSGR said in a statement.

In April, as part of a US corruption investigation into Guinea, FBI agents arrested BSGR agent Frederic Cilins on charges of witness tampering, obstructing a criminal investigation and destroying records. The trial is scheduled to begin on 2 December.