According to media reports, the Hungarian government is to decide whether to close its border to Croatia to curb the influx of refugees. In nearby Bulgaria, a migrant was shot dead, trying cross the border from Turkey.
Hungarian public broadcaster M1 reported on Friday that Prime Minister Viktor Orban had scheduled a meeting with his security cabinet for later in the day.
Fences have already been erected on the Hungarian-Serbian border, despite Hungary's membership of the so-called Schengen area, where border controls are largely abolished. Croatia and Serbia have not signed the agreement, however.
Afghan migrant shot dead
Reports of the potential border closure on Friday came hours after it emerged that an Afghan migrant had been shot dead near the southeastern Bulgarian town of Sredets, after trying to cross the border from Turkey.
"A big group of illegal migrants attempted to enter Bulgaria from Turkey. One man suffered a gunshot wound in the incident," a spokeswoman for the Bulgarian Interior Ministry told the AFP news agency late on Thursday.
Two border guards and a police officer reportedly intercepted some 50 illegal migrants who entered Bulgarian territory.
Bulgarian Interior Ministry's chief of staff, Georgy Kostov, said authorities have since opened and investigation info the incident.
The plan mostly deals with providing more aid to help Turkey host around 2 million refugees. Turkey is also the main starting point for the hundreds of thousands of refugees crossing the Mediterranean and entering Europe, with many EU officials pressuring the country to crack down on human smugglers.
The EU and Turkey also agreed to "speed up" the talks on easing visa restrictions for Turkish citizens, Juncker said.
Turkey had previously asked for 3 billion euros ($3.4 billion) in financial assistance, while the EU offered only 1 billion euros. According to Juncker, the financial details and a definite schedule for the plan to be implemented are still in the works.
German asylum reforms
Ahead of the summit on Thursday, German Chancellor Angela Merkel reiterated Turkey's role in solving the migrant crisis.
"Without a doubt, Turkey plays a key role in this situation," she said, adding that the EU wouldn't "be able to order and stem the refugee movement without working together with Turkey."