Fear that pent-up pressure could translate into violence led Austrian police to open barriers Thursday at a crowded migrant collection point. But any relief appeared temporary, with thousands more on their way in their search for safe haven from war and hardship.

The police move came just a day after thousands of migrants broke through police obstacles at the same collection center 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 Thursday followed instructions and regrouped outside the barriers but many continued walking northward away from the border. On the Slovene side, more than 1,000 migrants 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 migrants 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 Thursday, groups of migrants huddled around fires lit to combat the chill at Berkasovo village near a crossing point into Croatia. Niklas Stoerup Agerup of the U.N. refugee agency said the number of migrant families with children under the age of 5 transiting into Croatia has been increasing over the past several weeks.

Overnight and early Thursday "we've had a continuous flow of people coming in and also a continuous flow of people managing to cross the border," he said.

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 migrants.

"We can sit here, one day, two days without eat ... water, OK, 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 migrants 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 migrants 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.