Czech

MADRID, Spain (CNN) -- Spanish police have arrested 121 people and seized millions of computer files in the country's biggest operation against child pornography on the Internet, police said Wednesday.

Eight hundred police officers participated in the raids on more than 200 homes in most of Spain's provinces, a police statement said.

The operation was conducted in cooperation with federal police in Brazil, which uncovered a worldwide file-sharing network that was trading millions of files in 75 countries.

Spanish authorities have conducted a series of raids in recent years against child pornography rings, often with the assistance of overseas law enforcement agencies.

The police statement said two of those held produced the pornography and used members of their own families.

The statement added that UNICEF, the U.N. children's agency, has recently praised Spanish police over its outstanding work in tackling child pornography.