ATHENS, Greece (AP) — Greece’s conservative government has announced plans to overhaul the country’s migration management system, replacing existing open camps on the islands with detention facilities and moving 20,000 asylum seekers to the mainland over the next few weeks.

Deputy Defense Minister Alkiviadis Stefanis announced the changes Wednesday following a surge in the number of arrivals from nearby Turkey —with the number of migrants and refugees exceeding the islands’ populations in some cases.

Camps on Lesbos and four other islands in the East Aegean Sea are suffering dramatic overcrowding ahead of the winter, with hundreds of families sleeping in tents outside the official facilities.

The changes planned are the most significant since a landmark deal in 2016 between Turkey and the European Union to limit migration to Europe.