Tear gas has been used to disperse hundreds of migrants trying to break through a fence at Greece’s border with Macedonia.
The incident was near the Idomeni crossing, where more than 11,000 refugees and other migrants are camped out on the Greek side of the border.
There was some confusion over whether the Macedonian or Greek police were firing the tear gas, or both.
Balkan states closed off the migrant route to northern Europe this year.
This week Greece began deporting migrants who do not qualify for asylum, under an EU deal with Turkey.
in 2016, up to 7 April
37% of 2016 arrivals are children
53% arrive on Lesbos
366 died on Turkey-Greece route
853,650 arrivals in 2015
More than 300 people, many of them Pakistanis, were sent to Turkey by ferry from the Greek islands.
In addition, nearly 100 were deported via Greece’s land border with Turkey, AFP news agency reports.
More than a million undocumented refugees and other migrants have entered the EU by boat from Turkey to Greece since early last year, generating an unprecedented crisis for the EU’s 28 member-states.
Sunday’s unrest reportedly began after a group of migrants approached the fence to ask Macedonian border guards to open it and let them pass.
When their demand was rejected, they were joined by others, some of whom were carrying packed bags.
Migrants could be seen running from clouds of tear gas just inside the Greek border, as well as hurling stones across the fence.
An unnamed Macedonian police official told AFP: “Greek police are using tear gas near the border with Macedonia. It is calm so far on the Macedonian side of the border.”
However, Reuters news agency, also quoting an unnamed Macedonian police official, said migrants had thrown stones at the Macedonian police.
“The police fired tear gas in response,” the official said.
“The migrants were pushing against the fence but standing on the Greek side of the border. The fence is still there, they have not broken through.”
Aid organisations said they were treating people for tear gas exposure. “We have injuries and are extremely busy,” an MSF official told Reuters.
A note on terminology: The BBC uses the term migrant to refer to all people on the move who have yet to complete the legal process of claiming asylum. This group includes people fleeing war-torn countries such as Syria, who are likely to be granted refugee status, as well as people who are seeking jobs and better lives, who governments are likely to rule are economic migrants.
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