Sylvester Stallone Photo: VCG

A Bulgarian criminal gang used a fake passport in the name of the Hollywood actor Sylvester Stallone to advertise its counterfeiting services to potential clients, prosecutors said Friday.

Four gang members were charged for counterfeiting-related crimes with two other men charged on other offences, prosecutors said in a statement.

The passport in Stallone's name - giving the "Rocky" actor Bulgarian nationality - was found during a search of one of the gang members' homes in the central city of Plovdiv. 

Prosecutors believe it "was shown to customers as an example of the high quality of their workmanship" in faking documents.

The search was part of a police operation conducted earlier this week in several Bulgarian regions with the participation of agents of the US Secret Service and assisted by Europol.

Apart from the Stallone passport and other fake Bulgarian identity documents and drivers' licences, thousands of high-quality counterfeit 100-euro and 50-dollar bills were seized.