IDOMENI, Greece (Reuters) - Migrants cradling young children blocked a Greek motorway on Wednesday demanding onward passage to Macedonia, part of a growing bottleneck of refugees stranded by new border controls that have put Athens on a collision course with its EU peers.

A migrant holding a child cries next to a border fence at the Macedonian-Greek border in Gevgelija, Macedonia February 24, 2016. REUTERS/Marko Djurica

Families chanted “We want to go” after police stopped their convoy at Tempe in central Greece and authorities elsewhere in the country stepped up measures to control the flow of people trying to reach more prosperous nations further north.

Reuters journalists saw hundreds gathered at petrol stations and motels along the 530-km (330-mile) route from Athens to Macedonia, where guards periodically opened the border, letting 100 people through at a time.

Facing the problem of catering for more than ten times that number of new arrivals daily, Greece escalated protests against that restriction and others imposed by countries further along Europe’s main land migration route.

“It’s scandalous... that five police chiefs can overturn a decision of European Union prime ministers,” Migration Minister Yannis Mouzalas told Reuters in Athens.

Austria, Slovenia, Croatia, Serbia and Macedonia imposed controls after the heads of their police forces met last week.

Austrian Foreign Minister Sebastian Kurz brushed off criticism of his country’s plans to impose daily caps on migrants, saying on Wednesday that Greece needed to do more to reduce the flow.

More than one million migrants and refugees passed through Greece last year, many fleeing conflict in Syria and Afghanistan.

Another 1,600 arrived on the mainland from outlying islands bordering Turkey on Wednesday morning, and two Greek government officials said there were an estimated 20,000 stranded in the country.

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“When there is a bottleneck, the bottle could break, and where we had a controlled movement of individuals ... a broken bottle could result in an uncontrolled, illegal influx,” Mouzalas said.

‘YOU CAN DIE, JUST LIKE THAT’

A senior official of the UN refugee agency said the restrictions flew in the face of refugee protection laws.

“(They) ...probably go against even European rules and regulations and certainly against basic refugee protection laws,” UNHCR head Filippo Grandi told reporters in Athens.

In a conversation with German Chancellor Angela Merkel, Greek Prime Minister Alexis Tspiras expressed “deep displeasure” at the failure of EU member states to meet their commitments, a statement from his office said.

Balkan decisions to halt the flow would escalate, and not reduce, illegal migration, Minister Mouzalas added.

Meanwhile, Greek police had orders to stop buses carrying migrants to Idomeni, at the border with Macedonia, on Wednesday.

One driver in a convoy of eight buses told Reuters they were stopped by police and asked to sleep at a stadium on Tuesday night.

About 1,000 people were gathered in a field at the frontier on Wednesday, 24 hours after another group of migrants had been rounded up and removed from the area by Greek authorities.

At Athens’ Piraeus port, Syrian 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.”