Turkey and the EU have agreed a multibillion-euro deal to stem migrant flows into Greece, paving the way for Europe to take a far tougher approach towards irregular migration and instead accept more refugees directly from the war-torn regions.

Setting aside growing concerns about democracy in Turkey, a Brussels summit of EU leaders on Sunday night blessed a package offering Ankara fast-tracked visa privileges, €3bn in aid and the prospect of revitalised EU membership talks.

In return, Ankara has committed to a migration “action plan” to choke off the migrant flow into Greece and Bulgaria — a route used by more than 700,000 asylum seekers this year — offer some work rights to 2.2m Syrians, and also begin taking back some asylum seekers who crossed their borders into Europe.While laden with conditions, the bargain marks a significant step towards a more comprehensive European strategy on migration, which aims to throttle irregular migrant flows and increase incentives for asylum seekers to stay in Turkey or seek legal routes to Europe.

Chancellor Angela Merkel of Germany held talks with seven other EU leaders on the sidelines of the summit to explore what she described as “quotas” that would help “replace illegal migration by legal migration”.

The group has asked Jean-Claude Juncker, the European Commission president, to propose by mid-December a programme to directly resettle refugees currently in Turkey. This could potentially cover as many as 300,000 to 500,000 refugees, according to people familiar with the discussions.

While the scheme is expected to be voluntary — so no eastern European countries would be forced to accept refugees — paricipation could be tied to the sensitive debate over contributions to Turkey’s €3bn migrant fund, putting a bigger burden on those who do not take part.

Ahmet Davutoglu, Turkey’s premier, described the summit as a “new begining” in EU-Turkey relations that would help put relations on a path to ensure Turkish membership of the bloc was “not a dream but a reality”.

The meeting played out against a tense backdrop in Turkey, coming days after the arrest of two senior Turkish journalists at an opposition newspaper and growing unrest in the south-east prompted by the murder over the weekend of Tahir Elci, a prominent Kurdish lawyer.

The EU’s willingness to suppress its growing fears over Turkey’s political stability and the authoritarian tendencies of President Recep Tayyip Erdogan reflects the high premium placed on Ankara’s co-operation, particularly as Germany tries to reframe policy around migration.

Senior German officials are convinced Mr Erdogan can quickly crack down on Turkey’s booming people-smuggling trade. Alongside the emerging border fences to control and interrupt the migrant trail across the western Balkans, they hope the measures will dramatically reduce the inflow of migrants to Greek islands by the spring.

The full enforcement of a “readmission agreement” with Turkey would also open the option of sending back to Turkey migrants whose asylum applications are rejected.

Speaking before the summit, Donald Tusk, the European Council president, warned against any “naive” expectations that Turkey alone will solve Europe’s crisis, saying the bloc “cannot outsource” border control. “Without control on our external borders, Schengen will become history,” he said, in reference to Europe’s passport-free travel area.

Mr Davutoglu also made clear that he could offer no guarantees on stemming the flow of migrants. “Nobody can guarantee anything,” he said. “I wish I could say the numbers will decline but I cannot because we don’t know what will happen in Syria.”

For both the Turkish and EU sides, one of the main concerns over the migration deal is the danger of high expectations being dashed during implementation.

Elements of the deal are left deliberately ambiguous, including the time period for the €3bn payment and the format for twice-yearly summits between Turkey and the EU. While some EU states see this as a one-off payment, Mr Davutoglu suggested the EU finance setting a “burden sharing” precedent as Syria’s war played out.

Two of the most significant concessions for Turkey — visa liberalisation and the opening of several new chapters in its EU membership talks — are also largely tied to a political settlement in Cyprus. Nicosia has blocked accession talks and has demanded full recognition by Turkey as a condition of granting new visa privileges.

Mr Juncker said that he was “quite optimistic” about a breakthrough as soon as the spring, and officials attending the summit said the tone of discussions over Cyprus was especially encouraging. However, the island’s 40-year dispute has proven one of world’s most intractable diplomatic disputes.

Diplomats also warn that, even with a Cyrprus settlement, doubts remain over whether EU leaders will muster the political will to give 75 million Turks visa-free access to the Schengen area, particularly against the backdrop of elections in France and Germany.

In light of the Paris attacks, Dorothée Schmid of the Paris-based Ifri think-tank said ““it would be suicidal for a French government to give the Turks this visa liberalisation”.