Hungary is to seal its border with Croatia from midnight in a bid to halt the influx of migrants.
The move was announced by the country's foreign minister Peter Szijjarto, who said he expects the number of refugees to "slow to a trickle" after shutting the crossing.
He said EU leaders meeting in Brussels had failed to decide on a common force to safeguard Greece's borders and that Hungary had to protect the external frontiers of the EU's passport-free Schengen zone.
Migrants would be able to submit asylum requests at two transit zones to be set up on the border with Croatia, and crossing will only be possible via official border stations.
A razor-wire fence has already been erected along the border with Croatia.
Meanwhile Poland's Prime Minister Ewa Kopacz said on Friday she would send border guards and equipment to help Hungary seal its border with Serbia where thousands of migrants are passing.
Hungary had already clamped down on its frontier with Serbia, putting up a similar barrier last month.
Since then, refugees have been travelling via Croatia to reach Hungary.
More than 380,000 migrants have entered Hungary this year, nearly all passing through on their way to Germany and other countries further north in the EU.
It comes after Bulgarian border guards shot and killed a migrant trying to enter the country from Turkey.
The man was travelling with a large number of people from Afghanistan when he was shot near the town of Sredets and died on his way to hospital, a Bulgarian interior ministry official said.
"Our border patrol of border guards and police in the area had stumbled on 50 offenders, who illegally entered the country," Georgi Kostov said on national radio.
He added: "They put up resistance during the arrest.
"One of the officers fired warning shots and, in his words, one of the migrants was wounded by a ricochet and later died."
The rest of the group, aged between 20 and 30, were all detained, Mr Kostov said.
The Bulgarian Prime Minister left the EU summit he was attending in Brussels early after being told about the shooting.
EU leaders met to agree a united approach to secure the group's external borders which would involve the extended use of the European border force, Frontex.
They described agreement on a border "management system", with EU Council President Donald Tusk saying: "Frontex (is) to be given right to return irregular migrants on its own initiative and become more proactive in protecting external borders."
Bulgaria is not the favoured route for migrants.
Most travel further west through the so-called Balkan corridor from Greece through Macedonia, Serbia and Croatia.
But the Bulgarian border incident illustrates how hard the EU's plan will be to implement.
In separate developments, Mr Tusk expressed "cautious optimism" over agreement on how to handle the ongoing crisis.
A deal with Turkey is designed to stem the flow of migrants to Europe but it is not yet clear if it will work.
In the deal, Turkey asked for £2.3bn in aid as well as concessions on visas for Turkish citizens entering the EU and on Turkey's quest to join the EU.
Talks with Turkey, which the EU agrees is key to solving the crisis, will continue for several more days.
It is not yet clear how migrants can be persuaded to stay in Turkey rather than travel to Europe.