Thousands more migrants, many from Syria and Iraq, streamed into Croatia on Saturday on a journey fueled by hopes of a better life in Europe.
The influx, described by authorities as unprecedented, came a day after Croatia lifted its border blockade with Serbia, ending a weeklong standoff that had severely strained relations between the two Balkan countries.
It also came two days after an emergency European Union summit convened to address the largest movement of humanity on the continent since the end of World War II.
Within hours of the border opening, an estimated 10,000 migrants had crossed into Croatia. Authorities in Zagreb said 65,000 migrants had entered the country of 4.5 million residents in the past 10 days.
The French news agency AFP quoted Croatian authorities as saying the government might temporarily house the new arrivals at a former Yugoslav army base in the south of the Adriatic country.
Separately Saturday, a poll in Germany showed Chancellor Angela Merkel's popularity declining in recent weeks as she has sought to welcome hundreds of thousands of migrants.
Germany is expecting to receive up to 1 million migrants by year's end.
German authorities said 200,000 asylum requests had been received in the first half of this year, with 40 percent of them filed by people from Albania, Kosovo, Macedonia and Serbia, fleeing unemployment and poverty in hopes of a better life elsewhere.
Friday in New York, Slovenian Prime Minister Miro Cerar told the U.N. Sustainable Development Summit that the migration crisis required "urgent action" that addressed the "root cause" of the dilemma.
Cerar said Slovenia and other European countries were striving to resolve the crisis in Europe with "humanity and solidarity, but also security."
"We should pool our efforts in combating illegal migration and suppressing the trafficking of migrants and human beings," he added.