BARCELONA, Spain Spanish police seized an estimated 7.5 million euros (6.7 million dollars) worth of forged artwork and arrested seven, Catalan police officials said on Monday.

Intercepted merchandise included copies of paintings, lithographies and silk screen prints by Joan Miro, Pablo Picasso, Salvador Dali, Marc Chagall, Eduardo Chillida, Roy Lichtenstein and Andy Warhol, said police.

The operation -- nicknamed "Artist" -- resulted in six arrests in Barcelona and one person in Bilbao, who was deemed responsible for selling items in a gallery there.

According to an AFP report, investigations had also taken place in Madrid, Barcelona, Murcia and Bilbao, police said.

But they failed to arrest any forgers -- who are allegedly based outside Spain -- and they have yet to determine whether more art galleries were implicated in the affair.

Authorities responsible for protecting Spain's heritage initiated the investigation in 1998 after spotting growing numbers of lithographies by Spanish painter Joan Miro.

The artwork, they said, was well forged and smuggled into Germany, Switzerland, France, Italy, Scandinavian countries, the United States and Japan, sometimes with documents guaranteeing their authenticity.