EU leaders have offered Turkey a deal aimed at stemming the flow of migrants to Europe.

The agreement was made with Turkish President Tayyip Erdogan at a summit in Brussels and includes a possible €3 billion in aid.

The Turkish President will co-operate on improving the lives of two million Syrians in Turkey and encourage them to stay put.

In return, the European Union's offering easier travel for Turkish citizens to the EU and Turkey's joining the European Union was also discussed.

European Commission President Jean-Claude Juncker says there are two main objectives: "Ensuring refugees who are in Turkey to stay in Turkey" and preventing refugees from travelling through Turkey to come to the European Union."

They have also agreed to coordinate border controls to slow the influx of migrants crossing Turkey from Asia.

German chancellor Angela Merkel, who will visit Ankara later this week, said it was clear that Europe's efforts to filter and process refugees would not work without Turkey's cooperation.

"The hotspots alone won't solve the problem," she said.

Meanwhile, reports in Bulgaria said border guards shot at migrants attempting to cross from Turkey.

One Afghan man is said to have been shot dead near the town of Sredets.

The incident prompted Bulgaria's Prime Minister to abruptly leave the EU summit in Brussels.

Meanwhile, EU leaders have put pressure on the British Prime Minister to set out exactly what the UK wants from EU reforms.

David Cameron has agreed to offer clarity in a letter to the European Council President next month, ahead of a referendum in Britain on EU membership.