At least 260 refugees were injured on Sunday when Macedonian police used tear gas to push back hundreds of refugees from a border fence at a sprawling refugee camp, Idomeni on the Greek side of the frontier on Sunday.
"Two hundred people were treated by our medical unit for breathing problems, 30 for wounds caused by plastic bullets and 30 for other injuries," MSF official Achilleas Tzemos told AFP.
The escalation in tensions that have been simmering for weeks came after more than 500 people gathered at the fence at Idomeni, where more than 10,000 migrants and refugees have been stranded since February after a cascade of border shutdowns throughout the Balkans.
More than a million people fleeing conflict poured into Europe mainly through Greece in the past year. The European Union is implementing an accord under which all new arrivals to Greece will be sent back to Turkey if they don't meet asylum criteria.
A Macedonian official who asked to remain anonymous said that a large group of refugees left Idomeni camp on Sunday morning and stormed towards the fence.
Aid organisations said they were treating people for tear gas exposure. "We have injuries and are extremely busy," a senior official for medical charity MSF told Reuters. Another aid organisation also confirmed injuries among the refugee population.
Reuters witnesses said that unease stirred among the refugee population after a small group of individuals attempted to talk to Macedonian border guards and ask for the outpost to be opened. After they received a negative response, other individuals -- including some with packed bags -- started walking towards the fenced border.
Refugees at Idomeni are demanding that the border with Macedonia be opened, but no refugees have been allowed through for weeks.
Greek authorities have been trying to convince the population to move to reception camps, but refugees have been resolutely refusing to move.