The U.N. human rights chief is criticizing the Czech Republic for its policy of detaining migrants and refugees for up to 90 days.

Zeid Raad al-Hussein says credible reports indicate "the violations of the human rights of migrants are neither isolated nor coincidental, but systematic" in the country. He said the Czech measures appear to be designed to deter arrivals.

His office took aim in particular Thursday at detention facilities such as Bila-Jezova north of Prague, saying that even Czech Justice Minister Robert Pelikan has called it "worse than a prison." It cited an internal Czech report on Oct. 13 saying 100 children were inside when the rapporteur visited.

Zeid's office cited other reports that authorities had strip-searched some migrants to confiscate money to pay for their involuntary detention.

Austria's state rail company has suspended traffic near the main border crossing point with Slovenia so as not to endanger migrants near the tracks.

The move comes after Austrian police removed barriers Thursday at the migrant collection point at the Spielfeld crossing, saying they needed to relieve growing pressure due to overcrowding that could lead to violence.

Police say more than 3,000 migrants remain grouped near the collection point. But hundreds are scattered, with many walking northward from the border on a main road toward the southern city of Graz.

A U.N. refugee agency field officer says a large number of families with small children have been among the thousands of migrants crossing along a muddy border passage between Serbia and Croatia.

Niklas Stoerup Agerup, field protection officer for the United Nations High Commissioner for Refugees, said Thursday that some 1,000 people have passed through the border area overnight.

Stoerup Agerup says that around 60 percent of the people passing through are in families, and "maybe 45 percent of them have been children under the age of 5." He adds that "it is a tendency that we have been seeing over the last couple of weeks."

Croatian police say some 1,300 migrants have crossed the border since midnight Wednesday.