About 5,000 refugees and migrants reached Slovenia from Croatia in a single day, the Slovenian interior ministry has said, accusing Croatia of ignoring its requests to contain the flow.
Bostjan Sefic, state secretary at Slovenia's interior ministry, said Germany was accepting fewer arrivals, meaning Austria was in turn was asking Slovenia to limit the number of refugees moving through its territory.
"So far about 5,000 migrants arrived in Slovenia today," Sefic told a news conference on Monday.
"We expect another train with 1,200 migrants, which would mean more than 6,000 today. Croatia is ignoring our pleas, our plans."
Refugees travelling through the Balkans risk freezing to death as winter begins, the president of the European Commission has warned.
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Ministry of Defence says HMS Richmond has arrived to join patrols off the coast of Libya aimed at stopping human traffickers.