Authorities in the Balkans continue to scramble to stem the flow of migrants and cope with thousands of recent arrivals.
EU-member Croatia, the latest hotspot in Europe's migrant crisis, says it is overwhelmed with refugees and suggests it will redirect them toward Hungary, which is itself extending a recently built fence on its southern border to include its frontier with Croatia.
Croatian Prime Minister Zoran Milanovic said on September 18 that Croatia would begin helping migrants "move on."
Asked whether that meant allowing them to pass through to Slovenia, Milanovic said Hungary is "much closer."
He said the Croatian border would not be shut completely, but that it had reached its limit.
Hungarian government spokesman Zoltan Kovacs described Croatia's decision as "totally unacceptable."
Milanovic's comments came as Croatia closed seven of eight road crossings with non-EU member Serbia, which has funneled through huge numbers of Syrians and other migrants seeking to reach western Europe.
The crossing on the main road linking Belgrade and Zagreb appeared to be the only one left open to traffic on September 18.
The ministry said Croatia's army was also put on alert to deal with 13,000 migrants who have entered the country in the past two days.
Belgrade, fearing the closure in Croatia would block thousands of migrants inside Serbia, protested the move.
Aleksandar Vulin, Serbia's minister in charge of migration, warned "Croatia and every other country that it is unacceptable to close international roads."
"We will seek to protect our economic and every other interest before international courts," Vulin said.
The migrants began heading for Croatia after Hungary sealed its border with Serbia earlier this week, cutting off a key route into the European Union used this year by more than 200,000 migrants, many of them fleeing violence in the Middle East and Afghanistan.
Croatia had said it would let people pass through freely on their way to other EU countries, but Interior Minister Ranko Ostojic said the country's capacities were now "saturated."
Croatian authorities have been transporting many refugees to reception centers around the capital, Zagreb, after registering them.
But Hungarian media reported on September 17 that migrants were crossing from Croatia into Hungary, thus avoiding the razor-wire fence on Hungary's border with Serbia.
Prime Minister Viktor Orban said Hungary began work overnight on a fence on its border with Croatia and has already deployed hundreds of soldiers and police on the border.
Orban said a fast-solution fence will be finished by the end of September 18 on the 41-kilometer stretch of the border, where the two countries are not divided by a river.
Hungary is also planning a fence on its border with Romania.
Slovenia, which is next in line as the most likely route for migrants traveling to Austria and Germany, announced late on September 17 that it had stopped a train from Croatia carrying migrants and would return some 150 passengers to Zagreb because they did not have the necessary documents for onward travel.
Slovenia also suspended all train traffic between Slovenia and Croatia until September 18, the Slovenian STA news agency reported.
Slovenian Prime Minister Miro Cerar has said his country will stick to the rules of Europe's Schengen zone of border-free travel. It will receive asylum requests but not create a "corridor" for refugees to simply pass through Slovenia into Austria.
The 28-member EU has been unable to decide how to deal with Europe’s biggest influx of migrants and asylum seekers since World War II, leading Germany, Austria, and Slovakia to re-impose checks on parts of their borders.
Bulgaria began deploying 1,000 troops to the Turkish frontier, where several hundred people spent a third day stuck near a border city.