Law enforcement authorities in four Russian regions arrested 20 people suspected of operating scam call centers allegedly coordinated from Ukraine, the FSB security service said in a statement on Friday.

The arrests took place in the regions of Moscow, Novosibirsk, Tomsk and Altai, in a joint operation by the FSB and officers from the Interior Ministry.

According to the FSB, the call centers targeted Russian citizens in fraudulent schemes and were responsible for at least 33 documented cases of telephone fraud, defrauding victims of more than 200 million rubles ($2.5 million) in total.

“To carry out their criminal plans, the perpetrators recruited Russian nationals from disadvantaged and low-income communities in the Novosibirsk region as accomplices,” the law enforcement agency’s press service said.

Authorities said they seized electronic devices, unregistered firearms, cash, drugs, luxury vehicles and jewelry during the arrests.

Two people, who were not named, have been charged with organizing a criminal group and committing large-scale fraud, while the other 18 face charges of participating in a criminal organization and large-scale fraud.

In a similar operation last December, the FSB said it dismantled a scam call center accused of defrauding 100,000 people across 50 countries, including EU member states.