Hundreds of migrants have rushed at Macedonian border forces inan attempt to enter the country from Greece.
The security forces beat back the migrants with truncheons and riot shields. A number of people were injured.
On Thursday, Macedonia declared a state of emergency to cope with migrants - many from the Middle East - who are trying to reach northern EU states.
The UN urged both Greece and Macedonia to tackle a "deteriorating situation".
'Vulnerable categories'Some 44,000 people have reportedly travelled through Macedonia in the past two months, meeting little border resistance, but razor wire has now been rolled across the frontier to prevent people from entering.
The BBC's James Reynolds, at the scene, says hundreds of migrants crushed their way towards the border's security forces on Friday afternoon.
Medecins Sans Frontieres said it treated 10 people with wounds from stun grenades fired by Macedonian troops, near the Greek border village of Edomeni.
Amnesty International deputy Europe director Gauri van Gulik said: "Macedonian authorities are responding as if they were dealing with rioters rather than refugees who have fled conflict and persecution."