Greek police said on Sunday they had arrested nine suspected people smugglers in the north of the country over Easter.
Three of the suspects had detained 16 mostly Pakistani migrants, including three minors, at a camp near the port town of Thessaloniki, a police officer said.
The people smugglers demanded €2,500 to let them travel on to central Europe.
Six other alleged people traffickers were arrested at the Albanian border.
Those arrested are suspected to be members of an international people trafficking gang.
Since the Balkan route was closed in March 2016, more than 62,000 people remain stranded in Greece.
Greek police discover small groups of migrants almost daily, as they attempt to travel north or west with the help of people traffickers, who promise to take them to central Europe.
Greek police are seen with some suspected traffickers in February this year.
