Greek police say they have arrested nine people on suspicion of running a criminal ring that sold newborn babies to childless couples.

A police statement issued Monday said the arrests followed an undercover operation by two officers who posed as a couple wanting to buy a baby. Police raided an apartment in the greater Athens area on Friday where the undercover officers had been led.

The statement alleged that ring members arranged to sell the officers a 4-day-old infant for 18,000 euros ($20,800). The baby's mother was one of four Bulgarian women arrested.

Police said another woman was pregnant and the others had recently given birth.

Police suspect the ring was active for at least the past eight months.