( CNN ) -- Police in Finland say they have arrested more than 20 men on charges related to the sexual abuse of children . The men are suspected of using the Internet to approach girls between the ages of 9 and 15 , engage them in sexual discussions and , in some cases , to meet for sex in exchange for money , cigarettes or alcohol , the National Bureau of Investigations said in a statement . The men acted alone , police said . It was not clear when the arrests were made . The agency 's statement did not say and police officials were not in the office to comment Thursday afternoon . At least one of the men , who range in age from 22 to 48 , has a history of similar crimes against children , the agency said . Three of those arrested have already been convicted and sentenced to prison , according to the statement . CNN 's Per Nyberg contributed to this report .
Police in Finland arrest more than 20 on charges related to child sex abuse . The arrests began with a single child in 2006 , police say . At least one of the arrested has a history of similar crimes against children .