Austrian authorities on Thursday said they had smashed a people-trafficking gang believed to have transported 1,800 migrants to Vienna since February.

The group was charging 250-300 euros ($270-320) per person to bring them from Serbia and Hungary, raking in more than 500,000 euros, Interior Minister Johanna Mikl-Leitner said.

Hungarian authorities on Wednesday said they had accepted an Austrian request to take over a probe into the deaths of 71 migrants found in a truck on an Austrian motorway in August.

Vienna asked Budapest last month to handle the case, because the 59 men, eight women and four children were thought to have suffocated while the lorry was still in Hungary.

Tensions mounted at the key southern gateway for thousands of migrants into Germany, with overstretched German and Austrian officials trading barbs as asylum seekers queued for hours in the cold at border posts.

"Yesterday, I was here from five o'clock in the morning to two o'clock the next night. But the police didn't open the border," said Murtaza, 18, an Afghan at one of the crossings, Simbach am Inn.

Austria said Wednesday it would build a fence along its border with fellow EU state Slovenia to "control" the migrant influx, in what would be the first barrier between two members of the passport-free Schengen zone.

Both countries have become key transit points for tens of thousands of refugees and migrants seeking to reach northern Europe, as they try desperately to outrun winter and get ahead of more potential EU border closures.

Bavaria's state premier Tuesday blasted Austria for waving on thousands of migrants to Germany without informing local authorities and called on Chancellor Angela Merkel to intervene.

"Austria's behavior is hurting our neighborly relations. We cannot and should not deal with each other this way," Horst Seehofer told the Passauer Neue Presse in an interview.

A human trafficker who crammed 42 migrants into just six square meters (65 square feet) in the back of a lorry was sentenced to three years in jail in Austria on Tuesday.

"It's not difficult to imagine what it was like with 42 people squashed into six square meters," presiding judge Xenia Krapfenbauer said, calling it an "atrocious case of trafficking".

A total of 12,220 people entered eastern Austria in the previous 36 hours as the migrant flow from the Balkans to northern Europe continued, police said Monday.

On Sunday, 8,540 people entered the country via the Nickelsdorf crossing point with Hungary, followed by another 3,680 between midnight (2200 GMT) and 7:00 am on Monday, they said.

Europe's migrants crisis was expected Sunday to help give a major boost -- and possibly even a shock victory -- to Austria's far-right Freedom Party in elections in the city state of Vienna.

Fifteen years after the FPOe under the late Joerg Haider stunned Europe by entering the federal government, polls put the party almost level with the center-left Social Democrats (SPOe) in Vienna.

An Austrian court on Thursday handed down jail sentences to three Chechen asylum-seekers -- a man, his wife and his mother -- for seeking to join Islamic State extremists in Syria.

The 20-year-old man, his 21-year-old wife and the man's 39-year-old mother were intercepted in Turkey. They said they were there to obtain medical treatment for the mother who suffers from depression and panic attacks.

A suspected driver of a truck with 71 dead migrants on board found abandoned on an Austrian motorway in August will be extradited to Austria, a court in Bulgaria ruled Tuesday.

"The Montana regional court has decided in favor of the extradition of Tsvetan Tsvetanov to Austria," Svetla Stanimirova, spokeswoman for the court in northwestwern Bulgaria, told AFP.