Clashes erupted between Hungarian riot police and refugees desperate to cross the border from Serbia on Wednesday, while others carved out a new route and headed for Croatia. The unrest left scores of police officers and refugees injured, authorities said. Serbia lodged a formal protest with Hungary over the use of tear gas on its territory, and Interior Minister Nebojsa Stefanovic said police reinforcements were being sent to the Serbian side of the border to help calm tensions. U.N. Chief Ban Ki-moon said he was "shocked" by Budapest's actions, as hundreds of people fleeing war and misery, many of them Syrians, remained stranded at Hungary's newly fenced-off border."We want to leave! We want to leave to Germany!" cried one French-speaking man at a migrants' protest at the border through a megaphone. "Open the door!" he added in English, with hundreds echoing his call.In the chaos, at least four children were separated from their families and apparently taken by police to a nearby border control building, right group Amnesty International said. "The families are desperate to be reunited with their children. Not only have they experienced the traumatic journey to the border and the use of force by the police - they have now lost the security of being with their parents," said crisis response director Tirana Hassan.Hungary also deployed three military vehicles mounted with guns some 100 to 200 meters from the border, an AFP reporter at the scene said.Meanwhile, thousands of migrants have begun pouring into Croatia, setting up a new path toward Western Europe after Hungary clashes. Croatian police said Thursday morning that some 5,650 migrants have come into the country since the first groups started arriving early on Wednesday. Authorities have been using trains and buses to transfer them to refugee centers in the capital, Zagreb, and elsewhere. Authorities said they are forming a special body to deal with the influx. Interior Minister Ranko Ostojic said the country has the situation under control. But he warned that "if huge waves start coming through Serbia we must consider different moves." Croatia represents a longer and more arduous route into Europe for the asylum-seekers from Syria and elsewhere who have been fleeing into Europe in the past months. But they have little choice after Hungary sealed off its southern border with Serbia on Tuesday and began arresting anyone caught trying to enter the country illegally.Croatia said yesterday it could not take in any more migrants, amid chaotic scenes of riot police trying to control thousands who have streamed into the European Union country from Serbia. Interior Minister Ranko Ostojic said Croatia would provide migrants with safe passage to reception centers around the capital, Zagreb, but that those not seeking asylum would be considered illegal immigrants.European Council President Donald Tusk has summoned EU leaders to an extraordinary summit next Wednesday to discuss migration and a proposed scheme to redistribute 120,000 asylum seekers across the bloc. European Union interior ministers failed on Monday to agree on a quota system designed to spread the burden of this year's huge influx of migrants into Europe, many of them fleeing conflict in Syria and Iraq. Tusk said in a tweet yesterday he had convened a summit on Wednesday Sept. 23 from 1800 CET (1600 GMT) to deal with the refugee crisis.The turmoil in the Middle East and the five-year war in Syria have led many people to flee the conflict in an attempt to seek security and shelter in more prosperous and peaceful countries, such as those in Europe. The EU border agency Frontex said on Tuesday that more than 500,000 refugees have crossed the EU borders so far this year, up from 280,000 in 2014.