BRUSSELS - The European Union on Sunday pledged incentives to Turkey in exchange for a clampdown on the flow of refugees and migrants into Europe as it scrambles to find ways to cope with the largest displacement crisis since World War II.

Turkey will receive $3.2 billion in additional aid to improve conditions for the more than two million Syrian refugees in the country as part of the deal, struck at an emergency summit in the Belgian capital. In return, Brussels expects an "immediate and substantial" reduction of arrivals on the continent, said European Council President Donald Tusk.

About 880,000 refugees and migrants have arrived in Europe by sea this year - largely from Turkey - risking their lives to flee conflicts in Iraq and Syria or to seek a better life. The influx has left the EU struggling to find a coordinated solution, prompted questions about the bloc's open-border policies and caused political friction among member states.

The political rhetoric surrounding the refugee crisis has sharpened in the wake of the attacks in Paris earlier this month, even though all the perpetrators identified so far have been French and Belgian nationals. The attacks, which killed at least 130 people, were claimed by the Islamic State militant group.

"Some seek shelter from war and persecution, others seek a better life, and a few seek to destroy our values," Tusk said in opening remarks before the summit. "This is not about the EU outsourcing its security and migration policy to Turkey."

But just how effectively Turkey will be able to patrol its sea border, from where desperate refugees set off on perilous journeys to nearby Greek islands en route to Europe, remains in question. Despite increasingly dangerous winter weather, 26 more boats arrived at the beaches of Lesbos as European leaders met Sunday.

"We expect the Turkish government to fight human smuggling and trafficking networks effectively on its territory, including through its coast guard," said Martin Schulz, president of the European Parliament.

As part of the deal, the EU has also promised to ease visa restrictions for Turks entering Europe and to reinvigorate discussions on Turkey joining the union. Prime Minister Ahmet Davutoglu described it as a "historic day" for Turkey's accession bid.