The prime minister of Serbia has called for a coordinated international effort to solve the migrant crisis.
Aleksandar Vucic warned that xenophobia and fear of extremists was on the rise since the Paris attacks that killed 130 people.
Vucic was speaking at the opening of a ministerial conference of the Organization for Security and Cooperation in Europe (OSCE) in Belgrade on December 3.
Vucic urged the gathered ministers to come up with joint conclusions and recommendations.
Fueled by the Syrian war, some 850,000 people have entered the EU this year in what has become Europe's worst refugee crisis since World War II.
Vucic says "hundreds of thousands of migrants" have passed through Serbia and other countries on the so-called Balkan corridor.
He added that "fear exists of (infiltration) of foreign terrorist fighters who joined the war in Syria and Iraq and that fear has been rising, along with xenophobia."
U.S. Secretary of State John Kerry and Russia's Foreign Minister Sergei Lavrov are among world leaders attending the conference.