The decision was taken after investigators said they had enough evidence that the suspects "carried out criminal activities," Spanish national radio said late on Monday.
Among the suspects still in custody is Gennady Petrov, believed to be the leader of the gang.
Two people have been released on bail, while five others were freed without posting bail on the condition that they remain in the country.
Twenty Russians suspected of being members of the so-called Tambov criminal gang and involved in laundering the proceeds from organized crime were arrested last week in Madrid and Barcelona, as well as Malaga, Valencia and the Balearic Islands.
The 'Troika' operation involved Russian, U.S., German and Swiss law enforcement bodies and around 400 law enforcement officers. Police found more than 500 bank accounts and hundreds of bogus companies which are believed to have been used by mafia members to launder money in Switzerland and Panama.
Some 12 million euros held in bank accounts belonging to gang members have also been frozen by the Spanish authorities. During the raids police also seized 23 luxury cars, over 200,000 euros in cash, a yacht, weapons and a number of pieces of art.
The Tambov gang hails from St. Petersburg and takes its name from the city in southwest Russia that its founders were born in. It is thought to have several hundred active members.