"Refugees arriving in Europe have recounted in horrific detail the atrocities they witnessed within their homeland," Kyller said. "As one mother told a CRS staffer, 'You wouldn't put a child on this boat unless it's safer than your home'."
"Many risk their lives for this new start," he added. Many are targeted by traffickers and suffer exploitation and abuse. Some have spent all their savings or go into major debt to reach Europe.
Most of the refugees seek to reunite with their relatives in countries like Germany or Sweden.
Kyller said that Catholic Relief Services' guiding principles includes solidarity. This is the idea that "loving (and helping) our neighbor has global dimensions."
"The Pope is the very embodiment of that principle," he said.
Before other European countries closed their borders to migrants, Greece had been struggling to keep up due to its fragile economy.
Over 150,000 refugees and migrants have arrived in Greece by sea so far in 2016. At the village of Idomeni, over 10,000 people who aim to move deeper into Europe are stranded near the Macedonian border.
"Following the closures, the situation has gotten even more severe," Kyller said. Conditions there "deteriorate by the day."
While the migrant crisis has caused security fears in parts of Europe, Kyller said that Greece is more focused on concerns related to the economy and the employment crisis.
Catholic Relief Services and its local partners like Caritas have helped over 300,000 people in Greece, the former Yugoslav Republic of Macedonia, Serbia, Croatia, Albania and Bulgaria.
"We continue to adapt our priorities to the evolving situation. The Caritas network is vast and well-integrated into each of the countries where we work. This fact helps us reach the least-served groups as well as the countries that support them," Kyller said.
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Support for migrants and refugees includes food, winter clothing, sanitation, temporary shelter, legal aid and assistance in language translation.
There have been immigrant protests and clashes with police in Idomeni in recent days. On Sunday about 300 migrants, including women and children, were injured when they tried to break through the border fence on the Macedonian border. Police fired tear gas and bullets at them.
Police have arrested 14 pro-refugee activists from Britain, Germany and other European countries. They accused them of encouraging hundreds of migrants to storm the fence, the New York Times reports. The activists allegedly thought the action would generate sympathy and help re-open borders.