Police have broken one of the largest drug-trafficking rings operating in Greece after seizing more than 4 kilos of heroin in Athens, authorities said on Saturday.

Police said they arrested three men, aged 19, 22 and 23, after an undercover police officer offered to buy a kilo of heroin for 11,000 euros.

When the suspects arrived at the Kifissos KTEL bus station and attempted to sell the drugs, police moved in and made the arrests, a source said.

During an inspection of the suspects’ home in Vyronas, eastern Athens, police uncovered the remaining amounts of heroin, 403 grams of cocaine, electronic scales and 520 euros in cash.

The gang is believed to have been smuggled narcotics into the country from Albania before selling them in Athens and Patras.