Hundreds of desperate migrants were Tuesday trapped behind a razor-wire fence erected by Hungary, as Germany's Angela Merkel called for an EU summit on the refugee crisis.

While European leaders squabbled over how to manage the continent's biggest migrant influx since World War II, the exodus from war-torn Middle Eastern countries claimed more lives.

Another shipwreck off Turkey killed 22 refugees -- among them four children and 11 women -- who had tried to reach Europe, where more than half a million people have arrived this year to seek safe haven.

Hungary's conservative Prime Minister Viktor Orban has tried to stop the migrant flow through Balkans countries with the hastily-erected fence along its Serbian border, completed Tuesday.

He announced plans for a similar barrier on its frontier with Romania.

In addition, Budapest made its first arrests under tough new laws punishing "illegal border-crossing" or damaging the border fence with prison terms of up to three years.

"Why are they doing this?" asked an Afghan woman holding a child on the Serbian side of the fence where some 300 people gathered, some searching in vain for an opening, as Hungarian riot police watched them from the other side.

"It was really bad last night," said Bashir, a 17-year-old Afghan schoolboy who had arrived an hour after the border closed at midnight. "It was cold, particularly for families with little babies," he told AFP.

The controversial measures are part of Orban's strategy to stem the flow of migrants -- more than 200,000 of whom have entered his country so far this year -- travelling from Greece and transiting through the western Balkans and Hungary, most of them headed on via Austria to Germany.

But the Hungarian fences sparked fears in Serbia of an unmanageable number of migrants.

The Balkan state's minister for refugees, Aleksandar Vulin, urged Hungary to reopen its border, "at least for women and children," speaking to AFP at the Horgos crossing, where around a hundred people were waiting for the frontier to reopen.

Hungary's moves have been sharply criticised, with the UN refugee agency saying it could be in violation of the 1951 Refugee Convention.

According to the Serbian media -- and confirmed by a UNHCR official on condition of anonymity -- migrants arriving in Presevo, the first port of call after crossing over from Macedonia, began heading for Croatia after the Hungarian crackdown.

Romania, which is a member of the EU but not of the passport-free Schengen zone, criticised the fence planned along its own border as "out of step with the spirit of Europe".

Human rights group Amnesty International charged that "meeting those fleeing conflict and persecution with razor wire, troops and draconian new laws, Hungary is showing the ugly face of Europe's shambolic response to the growing refugee crisis". (AFP)