Two dozen people, most of them Russian nationals, were arrested across Spain this weekend on charges that they had sexually exploited some 8,000 women since 2004, forcing them to work in brothels in major Spanish cities, the police announced on Saturday.

The leader of the alleged ring, Igor C., 40, is said to have been responsible for more than 70 percent of cases involving the sexual exploitation of Russian women.

Known by his aliases “Mark Knopfler,” “the Many-faced one” or just “the man,” Igor C. reportedly provided women to brothels in Almería, Barcelona, Madrid, Granada, Córdoba, Tarragona, Huesca and the Balearic Islands, police said.

He has also been charged with document forgery and employment crimes.

According to the investigation, the victims would travel to third countries from Russia — Poland, Hungary and Lithuania — and take flights directly to Madrid. In an effort for the women to remain legally in Spain, the ring would send their passports back to Russia, which were stamped falsely to show that they had left the Schengen zone and re-entered as tourists.

Authorities also confiscated some three million euros in property, goods and cash, including high-price automobiles, jewelry and watches.

Witnesses who cooperated in the investigation said that Igor C. was never seen. He had about 16 cellphones and was never in direct contact with the prostitutes.

Police picked him up in Granada.