Pope Francis on Sunday decried the deaths of 71 migrants in an abandoned truck in Austria, calling it an offense against "the entire human family."
"We entrust each of them to the mercy of God," the pontiff said in Rome, calling on world leaders "to cooperate with effectiveness to prevent these crimes."
Meanwhile, Hungary said it has arrested a fifth suspect, a Bulgarian, on suspicion of human trafficking in connection with the deaths of the 71 migrants, whose bodies were found in a refrigeration truck left behind on a highway. Three other Bulgarians and an Afghan had already been arrested.
As thousands of migrants continued to stream into Europe, the top security officials in Britain, France and Germany called for better processing of them by the end of the year at points in Greece and Italy after their passage from war-torn countries in Africa and the Mideast.
Interior ministers Thomas de Maiziere of Germany, Bernard Cazeneuve of France and Theresa May of Britain said the migrants should be fingerprinted and registered, so authorities can quickly identify which ones need to be protected.
French Prime Minister Manuel Valls said migrants fleeing armed conflicts and persecution must be welcomed into France. "Each asylum demand must be examined rapidly," he said.
But not all European countries have embraced the influx of migrants.
Hungary's right-wing Prime Minister Viktor Orban said he is taking a hard line on migrants because he said they pose a threat to European security, prosperity and identity. Budapest is building a 4-meter fence on its southern border with Serbia in an effort to block the migrants from reaching the European Union, with its passport-free passage among its 28 member nations.
Macedonia declared a state of emergency earlier this month in response to daily border crossings from Greece of some 3,000 migrants pushing toward western European countries.
In Macedonia Sunday, some 500 migrants boarded a train that leaves twice a day from the southern town of Gevgelija headed for Macedonia's southern border where they can cross over into Serbia.
From Serbia, as the migrants continue on their Balkan route to western Europe, the next country is Hungary.
Hungary requires the migrants to be fingerprinted before entering temporary camps, causing concern for some.
Mark Kekesi, a volunteer with the advocacy group Migrant Solidarity said the migrants "are afraid of the Hungarian fingerprint regime because they are well aware of the fact that if their fingerprint is recorded in Hungary, then legally there is the opportunity for any western European country to send them back to Hungary."
Hungary has become a bottleneck on the journey to the more affluent western European countries because it has been holding on to the migrants, even when western European countries have said they are willing to accept thousands.
Germany said 800,000 migrants could settle there this year, way more than a year ago.
Hundreds have drowned in the Mediterranean, and authorities expect those tolls, as well as fatalities from land smuggling, to increase.
On Friday, United Nations chief Ban Ki-moon said he was "horrified and heartbroken" by the latest migrant deaths, both on land and at sea.
In a rare statement issued directly under his name, Ban said the conflicts and repression that force people to flee their homelands must be resolved.
He called on European governments to offer "comprehensive responses" aimed at expanding "safe and legal channels of migration" that also demonstrate "humanity and compassion."
He also said the migrant tragedies require "a determined collective [European] political response."
Ban said he plans a “special meeting devoted to these global concerns” on September 30, during the annual General Assembly of world leaders at U.N. headquarters in New York.