Sergei Butorin, 36, and Marat Polianksy, 28, were arrested late Wednesday at a brothel in this northeastern Spanish town, a police statement said.
An international arrest warrant named them as the suspected heads of the criminal gang Orekhovskaya, according to the statement.
Butorin and Poliansky resisted arrest, pulling pistols, but officers overwhelmed them.
Spanish police said they had worked closely on the arrest with Russian officers who were sent to Barcelona.
Police also seized two pistols, two machine guns, ammunition, two luxury cars and fake documents in an apartment in Castelldefels where the two suspects were hiding.
Both Butorin and Poliansky are wanted in Russia on charges relating to 29 killings, including the slaying of six police officers and a prosecutor who was investigating the group. Other charges are extortion, robbery and belonging to an illegal group.
Russian authorities have already requested their extradition.
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