Volunteers in 140 vehicles, risking fines for violating human trafficking laws, head to Hungary to pick up refugees.
Austria has imposed new restrictions at its borders, as the country on the main route for refugees crossing the European Union by land struggled to cope with a backlog of thousands trying to reach Germany.
The AP news agency also reported on Tuesday that the temporary control imposed by Austria from midnight local time (2200 GMT) on the Hungarian border may also be extended to other nations.
Thousands of refugees have poured into Austria in recent days, rushing through Hungary ahead of a deadline that saw that country close its border with Serbia.
Earlier on Tuesday, Austria’s next-door neighbour, Hungary, declared a state of emergency, and shut its border with Serbia leaving many desperate refugees stranded at the border.
Almost 10,000 people have also been detained for illegally crossing the border from Serbia, police said.
Hungarian Prime Minister Viktor Orban has indicated that asylum requests from refugees trying to enter Hungary from Serbia will be rejected, because Serbia is a safe country where refugees do not risk war or persecution.
On Tuesday evening, Orban defended his decision in an interview with a Hungarian TV station.
“We are not going to seal the border hermetically. We are simply enforcing the laws which were already in force until now. Even until now, Hungary’s border should not have been crossed at any other place except the border crossings,” he said.
“If someone claims to be a refugee, he will be asked if he filed an asylum request in Serbia. And if he did not file it, since Serbia is a safe country, it will be rejected.”
Al Jazeera’s Andrew Simmons, reporting from the Hungarian border town of Roszke, said there is desperation among refugees at the border.
“It is more of a crisis now more than ever for the refugees,” Simmons said, adding that a fence is also being planned between the border of Hungary and Romania.
On Tuesday night, hundreds of refugees between the border of Hungary and Serbia carried handwritten signs and shouted their plea to authorities to let them through the gate.
Meanwhile, Serbia was talking to the Hungarian government about the build-up of refugees on their frontier, a Serbian government minister said, adding Budapest would “have to open the border”.
Aleksandar Vulin, Serbia’s minister in charge of tackling the refugee crisis, did not elaborate.
UNHCR spokeswoman Melissa Fleming said on Tuesday that it is likely that thousands of refugees will simply divert their route now that Hungary has closed its border with Serbia.
“We’re definitely in touch with different countries on contingencies and UNHCR is ready to move and assist different countries as best we can,” Fleming said.
“It’s going to be just as much a struggle as it has been for Macedonia and Greece.”
Over 200,000 refugees have reached Hungary so far in 2015, nearly all by walking across the southern border with Serbia.
On Tuesday, EU’s foreign policy chief Federica Mogherini is meeting with the UN high commissioner for refugees to discuss the crisis.
She called for unity in relocating asylum seekers across member states.
Al Jazeera’s Mohammed Jamjoom, also reporting from Roszke on the Hungary-Serbia border, said there were more soldiers and policemen than there were refugees at the crossing.
“There are at least a few hundred refugees begging authorities at that crossing point to let them cross over into Hungary,” Jamjoom said.
Fewer refugees crossed into Austria from Hungary after Budapest started to clamp down on the flow through the Balkan peninsula to the richer countries of northern and western Europe, Austrian police said.
On Monday, the last day before Hungary sealed off its Serbian border with a razor wire fence, a record 15,700 people arrived in eastern Austria via the border town of Nickelsdorf.
Some 2,500 people spent the night in tents at the Austrian border, which had been set up by the country’s army.
Hungarian police said on Tuesday that two crossings on the border with Serbia have been closed to all traffic as stricter rules about the entry of migrants are applied.
“Since 12:30 the Hungarian border to Serbia has been closed. This means that no new migrants will be crossing the border there,” Helmut Marban, from the regional Burgenland police, told Reuters news agency.