Thousands of people hoping for asylum in western Europe have trekked to Vienna from Austria's main border crossing point with Hungary after rail traffic was suspended due to overcrowding.

Austrian Federal Railways said it no longer has the capacity to deal with the thousands of people at the Nickelsdorf crossing wanting to board trains to the Austrian capital.

Once in Vienna, most have travelled on to Germany and other western EU nations.

Rail services between Vienna and the Hungarian capital Budapest were suspended on Thursday,

With no trains running, thousands of people set out on the major road linking the Nickelsdorf border crossing with Vienna, 40 miles away.

Austrian police spokesman Helmut Marban said there was "some kind of group dynamic" at Nickelsdorf that started with a few people beginning to walk toward Vienna and quickly developed into a large movement of people who pushed through police lines.

He said the A4 expressway had been closed to vehicles because of the dangers posed by the long line of people walking.

They started the trek despite buses and taxis being called to Nickelsdorf to ferry migrants to the Austrian capital, the main jump-off point for Germany and other western EU nations for the tens of thousands who have crossed from Hungary.

Police said 7,500 people crossed into Austria at Nickelsdorf on Thursday.

Meanwhile, thousands more refugees endured torrential rain as they crossed from Greece into Macedonia.

About 7,000 people made their way past police in camouflage jackets as they contended with poor weather and muddy conditions.

The sudden onset of autumn took tens of thousands by surprise along the Balkans route from Greece to Hungary, the main gateway to western Europe for more than 160,000 asylum seekers from Syria and elsewhere already this year.

As recently as last week, those making the epic journey, much of it on foot, were baking in a region-wide heatwave and free to sleep under the stars.

Now they are without shelter and struggling to keep camp fires burning, highlighting the inadequate support provided by several European governments at each border crossing.