Macedonia has said it will no longer let any migrants through its border with Greece, effectively blocking the Balkan route north.

European Union leaders will on Monday back closing down the Balkans route used by most migrants to reach Europe, diplomats said, after at least 25 more people drowned trying to cross the Aegean Sea en route to Greece.

Balkan countries at the front line of the migrant crisis say they could close their borders to avoid becoming buffer zones for new arrivals.

Shooting breaks out for a second day on Sunday in northern Macedonia after clashes in the restive Balkan nation left at least eight officers and 14 gunmen dead, police said.