By Euan McKirdy and Tim Hume
NATO's top general warned that the mass influx of migrants to Europe is allowing ISIS to spread "like a cancer," as the EU announced plans for 700 million euros in emergency aid to Greece to house and care for migrants.
The emergency funding proposal, which still requires approval, was announced Wednesday by European Commissioner for Humanitarian Aid and Crisis Management Christos Stylianides, who promised to "fast-track" the assistance.
"These are extraordinary times," Stylianides said. "We all need to step up our efforts with no delay to prevent a further deterioration of the situation."
The aid proposal -- intended to meet basic needs such as food, water and shelter over the next three years -- came a day after the United Nations High Commissioner for Refugees warned of a burgeoning humanitarian disaster in Europe, and NATO's top general told a Pentagon briefing that ISIS was exploiting the migrant crisis.
Following testimony to the Senate Armed Services Committee, U.S. Air Force Gen. Philip Breedlove told reporters that mass migration spurred by the ongoing conflict in Syria and the threat of ISIS in the Middle East was allowing terrorists free entry into the continent.
Breedlove, who is head of Supreme Allied Command in Europe, said the migration "masks the movement of criminals, terrorists and foreign fighters (into Europe)."
"Within this mix, (ISIS) is spreading like a cancer, taking advantage of paths of least resistance and threatening European nations, and our own, with terrorist attacks," he said.
UNHCR warns of 'imminent humanitarian crisis'
Elsewhere, the constant influx of migrants meant Europe was facing "an imminent humanitarian crisis," the United Nations High Commissioner for Refugees (or UNHCR), warned Tuesday.
More than 131,000 migrants had entered Europe in just the first two months of 2016 -- a number that was close to the total for the entire first half of 2015, according to UNHCR figures.
Europe's failure to mount a unified response to the situation meant it now faced a crisis "largely of its own making" as the number of migrants stranded in Greece rapidly increased, the statement said.
A number of European countries, including those along the main Balkan migration route through Europe, recently agreed to tighten border controls to slow arrivals to a trickle.
The move has created a rapidly growing bottleneck of migrants in Greece, a country facing its own severe financial hardships, as the flow of people there from Turkey continues unabated.
Tensions boiled over Monday at Idomeni, a major transit camp on the Greece-Macedonia border, as migrants were denied permission to cross into Macedonia. Macedonian authorities have been letting only a few hundred cross each day, and only Syrians and Iraqis with photo identification.
A group responded to the backlog by ramming through the barbed-wire border fence with a post.
The UNHCR says the number of migrants stuck in Greece had soared to 24,000 by Monday night, with about 8,500 of them stuck at Idomeni.
Merkel: Reinstate Schengen system
Also Tuesday, German Chancellor Angela Merkel said that rather than implementing extra border controls, European countries needed to reinstate the Schengen system of border-free travel within Europe to deal with the crisis.
At a news conference with Croatian Prime Minister Tihomir Oreskovic, she stressed that while there was a need to protect the European Union's external frontiers, it was important to reinstate the system of open borders between member states.
"The situation is not yet so that we can be content. Every day we see the pictures from Greece -- we have to get back to the Schengen system," she said, referring to 1985's Schengen Agreement, which guaranteed free movement within Europe. It has been temporarily suspended by some member states and is expected to be amended later this month.
"Greece of course has to protect its borders -- this is not about only protecting the Greek-Macedonian border from the Macedonian side, so that we don't get new routes in the migration flow."
She also urged EU member states to stick to their obligation, made in September, to resettle 160,000 refugees among themselves over two years. So far, only hundreds have been resettled.
Rise of European Islamophobia
Rights groups have cautioned against scapegoating refugees after violence like the deadly coordinated attacks in Paris in November 2015.
"Significant refugee flows to Europe, spurred largely by the Syrian conflict, coupled with broadening attacks on civilians in the name of the extremist group (ISIS), have led to growing fear-mongering and Islamophobia," Human Rights Watch said in its 2016 World Report.
Breedlove told the Senate Armed Services Committee that alongside the threat posed by extremist organizations in Europe was the potential for unrest from local nationalists opposed to the unprecedented influx of refugees from Syria, Afghanistan, Iraq and unstable parts of Africa.
Fears are they could become increasingly violent, building on the small number of attacks against migrant and refugee populations.
Russia: Contributing to instability
In his Pentagon appearance, Breedlove also pointed a finger at a "resurgent, aggressive Russia," which "poses a long-term and existential threat to the U.S. and our European allies."
Russia's continued involvement in the Syrian civil war, which Breedlove said had bolstered Syrian President Bashar al-Assad and his allies, has changed the dynamic in the theater and "complicated the problem ... in the air and on the ground."
The view is compounded by Pentagon reports that Russia is using the nascent, shaky ceasefire in Syria to seize key territory.
Relations between Turkey -- the only Muslim-majority member of NATO -- and Russia also threatened security, with tensions between the two increasing the "risk of miscalculation or even confrontation."