Thousands of migrants, mostly Syrian refugees, travelled through Macedonia and Serbia towards western Europe, as Italy's foreign minister said the escalating crisis threatened the bloc's "soul".
Macedonia said it would allow a limited number of "vulnerable" migrants to enter the country after sealing its border with Greece to them, leaving thousands of refugees stuck in no-man's land.
Macedonian political leaders agreed to hold elections in early 2016 in order to overcome a deep political crisis, EU enlargement commissioner Johannes Hahn said.
NATO head Anders Fogh Rasmussen said Wednesday the alliance will shortly offer Georgia closer ties, but made no mention of membership, amid growing concerns over Russia's intentions in Ukraine.
Six policemen were injured and 27 people were detained Tuesday when a peaceful protest over the death of a Macedonian teenager in Skopje turned violent, a police spokesman said.
Freezing temperatures and heavy snowfall in the Balkans, that seriously affected traffic throughout the region, claimed a second victim on Sunday as a man died from cold in northern Serbia.
Ban Ki-moon begins a tour of the Balkans this week which will include the first visit by a UN chief to the site of the 1995 Srebrenica massacre and to Kosovo since it declared independence in 2008.