Macedonian riot police used tear gas and stun grenades on Friday as thousands of migrants tried to enter the country from Greece, Sky News reported.

About 3,000 people from the Middle East, Africa and Asia tried to charge police officers after spending the night in the open in a no-man's land between the two countries after Macedonia sealed its southern border to migrants and refugees. Coils of razor wire have been rolled across the border, preventing migrants from entering, according to the BBC.

Macedonia declared crisis situation in two border regions on Thursday due to “an unprecedented flow of refugees from the Middle East” entering from Greece.

Refugees, coming mainly from Syria and Afghanistan are crossing Macedonia’s southern border from Greece near Gevgelija and then board a train that would take them to the country’s northern border with Serbia. From there, they attempt to enter Hungary, which lies at the southern edge of the EU’s passport-free travel Schengen zone, before moving to wealthier EU nations of western and northern Europe. About 44,000 migrants have reportedly travelled through Macedonia in the past two months.

The stepped-up border enforcement came after Greece picked up some 2,500 migrants from its islands of Kalymnos, Lyros, Kos, and Lesvos and landed near Athens on Thursday in a bid to relieve stress on the islands, where boats full mostly of Syrian migrants arriving via Turkey have led to a dangerous overcrowding of refugee centres. Most of the news arrivals were expected to travel north to the border with Macedonia.

Macedonian authorities said that official border crossings remained open but illegal border entry will be reduced to a minimum.

A group of about 200 migrants, most of them women, children and old people were allowed to enter Macedonia from Greece on Friday afternoon. Police escorted them to the railway station in the town of Gevgelija from where they were expected to board a train to Serbia.