SAMOS — Clashes broke out Thursday between police and a group of migrants at a refugee camp on the eastern Greek island of Samos, prompting the local mayor to shut down a nearby elementary school and kindergarten.

The clashes came as about 200 people began protesting conditions in the dramatically overcrowded camp and demanding they be allowed to leave the island.

The protesters threw stones and other objects at police, who responded with tear gas and stun grenades. Others living in and around the camp headed up the hill on which the camp was built to avoid the conflict.

Under a 2016 deal between the European Union and Turkey to stop migrant flows into Europe, those who arrive on Greek islands from the nearby Turkish coast are held in island camps pending deportation unless they successfully apply for asylum in Greece.

Only those deemed to be in vulnerable groups, such as the elderly, people with serious health problems and families with young children, are eligible to be moved to the mainland.

The deal, coupled with an increase in new arrivals since the summer, has led to deteriorating conditions in chronically overcrowded camps on the eastern Aegean islands.

The camp in Samos is now more than 11 times over capacity, with 7,497 people registered as living in and around the facility that was designed to house 648.

Greece’s 6-month-old government has vowed to move about 20,000 people off the islands and into other migrant and refugee facilities on the mainland by early 2020. But despite the transfer of several thousand people in recent months, the overcrowding continues to worsen as more newcomers arrive.