The leaders of Europe's biggest far-right parties have gathered in Austria's capital, Vienna, to join forces against the European Union, "radical Islam" and asylum seekers.

Hainz-Christian Strache, the leader of Austria's Freedom Party, warned refugees on Friday that Europe was ready to send them packing as he addressed a cheering crowd of about 2,000 people gathered at a convention centre.

"We will save you on the high seas," Strache said. "But we will send you back to the harbour where you started out."

He accused German Chancellor Angela Merkel of causing "irreparable damage" to Europe by opening German borders to hundreds of thousands of asylum seekers fleeing war in the Middle East.

"We are not against Europe as our opponents are always saying. We want another Europe, a better Europe, one of nations, values, culture and identity," Strache said. "The new fascism comes from the left and from radical Islam."

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Marine Le Pen of France's National Front expressed hope that Britain's June 23 vote on whether to remain a member of the European Union would give their cause new momentum.

"I support the referendum in the United Kingdom because I want all the countries in the EU to have this choice," Le Pen said.

"But even if we don't get Brexit, it will present a huge new problem for the European Union which has pledged to give Britain special rights if it stays that other countries won't have. So this could be the beginning of Europe a la carte."

Al Jazeera's Jonah Hull, reporting from Vienna, said it was no coincidence that the gathering was taking place in Austria.

"This was a country that just a month ago came within an electoral whisper of being the first country since the Second World War to elect a far-right head of state," he said.

Held under the slogan "Patriotic Spring - Cooperation for Peace, Security and Prosperity in Europe", the gathering also included politicians from the Alternative for Germany (AfD) and Northern League of Italy among others.

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Populist, anti-immigration parties are on the rise across Europe as high unemployment and austerity, the arrival of record numbers of refugees, and recent attacks in France and Belgium deepen voter disillusionment with traditional parties.

In neighbouring Germany, where far-right parties have struggled to gain traction in the post-war era, the AfD has won double-digit support in a string of state elections and seems poised to enter the German parliament, the Bundestag, in Berlin next year.