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

The decision came after Slovenia barred access to migrants transiting the country, and Croatia and Serbia then said they would follow suit.

Some 13,000 migrants are now stranded at the Macedonia-Greece border, while some 400 are stranded in a 'no-man's land' between Macedonia and Serbia.

"Macedonia will act according to the decisions taken by other countries on the Balkan route," an Interior Ministry spokesman told Reuters.

The moves come after the EU and Turkey set out a plan to ease Europe's biggest refugee crisis since World War Two.