By Yannis Behrakis
IDOMENI, Greece (Reuters) - Migrants cradling young children blocked a motorway in central Greece demanding onward passage to Macedonia on Wednesday, part of a growing bottleneck of refugees stranded by new border restrictions and closures across Europe.
Families chanted "We want to go" after police stopped their convoy at Tempe, as Greece stepped up measures to control the flow of people passing through its territory on their way to more prosperous countries further north.
Reuters journalists saw other groups gathered at petrol stations and motels along the 530-km (330-mile) route from Athens to Macedonia, where guards opened the border for an hour on Wednesday morning, letting just 100 people through.
Greece has protested against restrictions imposed by countries further north along the main land migration route into Europe, including along Austria's frontier with Slovenia and Macedonia's border with Greece.
Austrian Foreign Minister Sebastian Kurz brushed off criticism of his country's plans to impose daily caps on the number of migrants, saying on Wednesday Greece needed to do more to reduce the flow.
More than a million migrants and refugees passed through Greece last year, many of them fleeing conflicts in Syria and Afghanistan. Another 1,600 arrived on the mainland from outlying islands bordering Turkey on Wednesday morning.
Greek police were instructed to halt buses with migrants from heading to Idomeni at the border with Macedonia on Wednesday, an official said.
"Nobody will leave for Idomeni today. I will not allow a single bus to leave for the north until further notice that Skopje is allowing people through," Konstantinos Louziotis, head of the public order ministry's immigration department, told Reuters.
One driver in a convoy of eight buses carrying migrants to the Macedonian border told Reuters they were stopped by police and asked to sleep at a stadium.
About 1,000 people were gathered in a field at the frontier on Wednesday morning, 24 hours after another group of migrants had been rounded up and removed from the area by Greek authorities.
Under an overcast sky, people sat huddled in tents, burning fires to ward off the cold.
At Piraeus port, migrant Hasan Frnjari said authorities had told him to stay there until further notice.
"We came here in the morning and don't know what to do because we want to continue to Macedonia. Now they tell us the borders are closed," said the 23-year-old marketing student from the northern Syrian city of Aleppo.
"I don't think they really understand the cause we left from Syria, in Aleppo people are in danger. The city is under constant shelling. You walk in the street and you can die just like that."
(Additional reporting by Lefteris Karagiannopoulos, Writing By Michele Kambas; Editing by Andrew Heavens)