After risking his life to get out of Afghanistan, Jamshid is out of luck -- he arrived in Greece just as Balkan states further north shut their doors to Afghan nationals.

Now he and hundreds of fellow Afghans face an uncertain future at the Greek camp of Schisto, waiting for a path to Europe that may never reopen.

A Macedonian man suspected of recruiting jihadists for the Islamic State (IS) group was arrested on Friday in north-east Italy, police said.

The suspect, detained near Venice, was "in charge of selecting and recruiting aspiring jihadists... who were then to be passed on to a Bosnian imam to be radicalized, enrolled in a terrorist organization and transferred to a Middle Eastern war zone," investigators said.

Anxiety gripping his features, the man from Syria hands over his birth certificate to Macedonian border police, hoping against hope that it will be enough to allow him to continue his journey to northern Europe.

A Macedonian policeman, no older than 35, squints at the document for a couple of minutes, scanning it for signs of a possible forgery.

Austria's foreign minister warned Macedonia on Friday that it should be ready to close its border to migrants, saying that Vienna may also begin turning refugees away in coming months.

"The migrant ceiling that Austria has set for 2016 will likely be reached in the next few months and Austria will then stop migrants at its borders," said Sebastian Kurz, whose country has set a refugee cap of 37,500 for this year.

After a night on the Greek-Macedonian frontier in sub-zero temperatures, some 2,000 mainly Syrian refugees on Thursday resumed their tortuous trek to northern Europe that was temporarily blocked by a border closure by Skopje.

"I'm very happy the problem is resolved," said 19-year old Imad. "I want to go to Germany to study".

Greek police launched an operation early Wednesday to remove a thousand migrants gathered at the border with Macedonia, after Skopje introduced a system of filtering those who can cross the frontier by nationality.

Some 400 riot officers were mobilized at dawn, a police source said.

A migrant died of electrocution Thursday after clashes broke out between refugees and migrants trapped on the Greek-Macedonian border, Greek police said.

The man, believed to be from Morocco, died after climbing on to a carriage of a stationary train near the border and touching a high-tension cable overhead, local police spokesman Petros Tanos told AFP.

Macedonia started building a fence on its border with Greece on Saturday to better control the influx of migrants passing through the Balkan country, an AFP photographer at the frontier said.

The extent of the barrier was not yet known, but the photographer said the army was using heavy machinery to build a 2.5-meter-high (8-foot) fence near the crossing point used by migrants at Gevgelija.

Over 200 migrants on Thursday tried to break through barbed wire fences to cross from Greece into Macedonia, which imposed new border restrictions last week, throwing stones at police, AFP reporters said.

At least five of the migrants managed to get across in the assault as the crowd shouted "Open the border" to the Macedonia police ranged in front of them.

The number of migrants and refugees entering Macedonia from Greece has risen significantly, with 10,000 making the crossing in the past 24 hours, police said Thursday.

Since early September, the border has normally seen around 3,000 to 5,000 daily crossings by migrants, many of them fleeing conflict in the Middle East, heading to northern Europe hoping to start new lives.