Thousands of migrants are stranded in Serbia and Croatia as a result of Hungary closing its border with Croatia, authorities have said.

Many of those who want to move further north have found their new route through Slovenia blocked because the country says it will only take 2,500 people a day.

Thousands of people, many of them refugees fleeing war-torn Syria, have been making the perilous journey north to the EU's richer countries in the hope of settling there.

About 1,000 migrants have arrived in Austria from Slovenia since Hungary finished building a fence along its border, Austrian police have said.

Until the border was closed, upwards of 5,000 were passing through Croatia and Serbia and into Hungary every day.

On Sunday, Croatian police said nearly 6,000 people remained in the country unable to move forward.

Around 50 buses are parked up at Croatia's Opatovac refugee camp waiting to take the migrants toward Slovenia, and in Serbia, hundreds more people have been sitting in another 40 buses waiting to cross to Croatia.

The numbers waiting are expected to increase as more people travel along the so-called Balkan corridor that goes from Turkey to Greece and then through Macedonia, Serbia and Croatia.

European leaders have been trying to develop a co-ordinated response to the ongoing migrant crisis, but disagree on what approach is best.

On Friday, the Hungarian government closed the country's border with Croatia "to protect the citizens of Hungary and Europe". Hungary, which has received more than 383,000 migrants this year, has spent months building a razor-wire fence along its southern borders in a bid to keep them out.

Foreign minister Peter Szijjarto said EU leaders had failed to safeguard Greece's borders and that Hungary had to protect the external frontiers of the EU's passport-free Schengen zone.

A spokesman for the United Nations refugee agency warned Hungary's decision to close its border has increased migrants' suffering.

He said the problems are likely to get worse as the backlog continues to build.

Night-time temperatures are expected to fall below 10C in many parts of central Europe in the coming days.

Meanwhile, German Chancellor Angela Merkel has met Turkish leaders in a bid to agree a plan that could help stem the mass movement of migrants into Europe.

Under the plan, Turkey will try to stop migrants crossing to the EU in exchange for €3bn (£2.2bn) and a series of visa concessions.

Germany expects around 800,000 to a million people to arrive this year.