VIENNA (AP) — Migrants traded punches and scuffled with police at a Serbian border crossing with Croatia Thursday as pent-up pressures on their trek toward hoped-for safe haven in the European Union boiled over. The unrest at Berkasovo village subsided after several minutes but reflected frustrations of the tens of thousands of people facing long waits and other hardships as they make their way north over the Balkans each day in search of better lives in prosperous EU countries. Further along that route, Austrian police moved to relieve pent-up pressure which they feared could lead to violence, removing barriers at an overcrowded collection point at border crossing with Slovenia. A day earlier, thousands of migrants broke through police obstacles at the same collection center at the Spielfeld border point. Many of the migrants spilled out of the facility Thursday but then gathered nearby, following police instructions. But many others walked 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 EU nations. The flow of people over the so-called west Balkans route that begins in Greece has shifted. Migrants still cross first into Macedonia and then Serbia but now enter 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 migrants huddled around fires lit to combat the chill at Berkasovo village. 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 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 in 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 grouping Europe's centrist parties. Join the conversation about this story »