The European Union needs to brace for a possible "massive" influx of Syrian refugees, one of the bloc's top officials said Wednesday.

"We need to be prepared for the possibility of an even more massive influx," internal markets commissioner Michel Barnier said during a European Parliament debate on Syria.

Several EU nations including Bulgaria and Greece have reported a strong increase in refugees from the 30-month Syrian conflict.

More than two million Syrians have fled their country to seek refuge mainly in Lebanon, Jordan and Turkey, and the number could swell to 3.5 million by year's end, Barnier warned.

"The response surely should not be to close national borders, to shrink away or barricade ourselves," said Barnier, speaking as representative for the European Commission.

"This is not a strictly national issue, it is a European issue."

"Any crisis of this size affects us all and we must be ready in a spirit of great solidarity," he said.

After lawmakers adopted a resolution calling for a humanitarian aid conference to help neighbouring countries overwhelmed with Syrian refugees, Barnier said he too was in favour.

"We are in agreement on the principle (of the conference) and will have to see how to organise it," Commission spokeswoman Pia Ahrenkilde-Hansen confirmed in Brussels.

The UN High Commissioner for Refugees has asked EU nations to offer asylum to 10,000 Syrians and resettle 2,000 of the most vulnerable.

Some 50,000 Syrians have applied for protection since the beginning of the conflict in March 2011, mostly in Sweden and Germany.