Austrian police have opened barriers at a crowded refugee collection point amid fears that the situation could turn violent.
The police move came just a day after thousands of refugees broke through police obstacles at the same collection centre at the Spielfeld border crossing with Slovenia.
This time, police said they removed barriers to relieve pressure that could have triggered violence among those waiting for transport to shelters.
They said some of those involved followed instructions and regrouped outside the barriers but many continued walking north away from the border.
On the Slovene side, more than 1,000 refugees were waiting for entry, either to apply for asylum to Austria or to transit to other prosperous EU countries further north.
The flow of people over the so-called west Balkans route has shifted, with refugees now entering Croatia instead of Hungary, which erected a fence along its border to Serbia.
From Croatia, they move to Slovenia, which has struggled to deal with the increasing numbers.
In Serbia, groups of refugees huddled around fires in cold weather conditions at Berkasovo village near a crossing point into Croatia.
Niklas Stoerup Agerup of the UN refugee agency said the number of refugee families with children under the age of five transiting into Croatia has been increasing over the past several weeks.
He said: “We’ve had a continuous flow of people coming in and also a continuous flow of people managing to cross the border.”
Fadl Abdul, a Palestinian from Lebanon was among those warming himself at one of the fires. He said the children were particularly vulnerable to the hardships faced by the refugees.
“We can sit here, one day, two days without eat ... water, okay, no problem,” said the 43-year-old. “But what about the kids?
They need milk, they need to change clothes, everything.”
Croatian Interior Ministry spokesman Domagoj Dzigulovic said 1,277 people arrived to Croatia from midnight until late Thursday morning.
Further north, authorities in Slovenia counted 12,616 refugees entering the country on Wednesday.
Slovenian authorities say they can handle no more than 2,500 entries per day, and have accused Croatia of sending too many refugees through.
In Madrid, an EU People’s Party congress urged swift action.
“The right to seek asylum must be respected for those in need of protection, while swift and effective return and readmission measures for those not qualifying must be put in place,” said an “emergency resolution” adopted by the congress.