41 suspects quizzed over £130m Costa money laundering

Seven lawyers and three notaries were among those detained last week in a crackdown on the operation, which was centred in the southern Spanish resort of Marbella.

The interior ministry described the ring as the largest operation of its kind ever uncovered in Spain.

Police said that they had seized 251 plots of real estate, a ship, two small planes and 42 luxury cars as well as documents and hard discs from computers.

Those being questioned were from Spain, France, Morocco, Finland, Russia and Ukraine, the authorities said, although none was identified by name.

The group was suspected of laundering millions for gangs involved in murder, drug trafficking, arms dealing and prostitution in Marbella and other centres on the Costa del Sol, which is considered a base for organised crime groups dealing in everything from stolen cars to illegal weapons.

On Saturday, the interior ministry said the authorities suspected that some of the money had been illegally siphoned from Yukos. Large sums are thought to have been diverted from the Russian oil company to a Dutch firm and then reinvested in a Spanish outfit.

A statement said the Spanish judicial authorities had worked closely with the Russians on the case, dubbed "White Whale", which involved more than 300 police officers.

In Moscow, Yukos has denied reports that it might have been involved in any money laundering scam. Alexander Shadrin, a company spokesman, told Ekho Moskvy radio that such reports were "nonsense".

"The only place left to look is on Mars - did we launder something there?" the station quoted Mr Shadrin as saying.

That was a sarcastic reference to the Russian government’s campaign of accusations and tax claims against the beleaguered company.

Yukos has been targeted by the Russian authorities in a legal campaign widely seen as punishment inflicted by President Vladimir Putin’s Kremlin for the economic clout and political ambitions of its founder and former chief executive, Mikhail Khodorkvosky.

The company’s biggest production unit was sold by the state in a disputed December auction to pay part of the 14.5 billion that the authorities say Yukos owes in back taxes.

Khodorkvosky has been in prison since his arrest in October 2003, and he is to be tried on fraud and tax-evasion charges which are separate from the allegations against the company.