ZAGREB/BELGRADE: Former Yugoslav foes Serbia and Croatia turned back the clock on 15 years of reconciliation on Thursday, trading embargoes and insults as Europe’s migrant crisis damaged relations in the fragile Western Balkans.

With relations hitting their lowest ebb since Serbia came in from the cold with the ouster of late strongman Slobodan Milosevic in 2000, the Balkan neighbors exchanged tit-for-tat sanctions that saw Croatian goods and cargo vehicles banned from entering Serbia and Serbian-registered vehicles barred from entering Croatia from Serbia.

Croatia, which fought a 1991-95 war against Belgrade-backed Serb rebels to forge its independence from communist Yugoslavia, is demanding Serbia stop directing tens of thousands of migrants exclusively over their joint border, saying it cannot keep pace with the influx.

Amid conflicting information from both sides, Serbian citizens were also being turned back at the Croatian border, witnesses said, though Croatia’s interior minister blamed a glitch in the computer system.

Serbia was unconvinced, and in language that reached back to the collapse of their joint Yugoslav state two decades ago, the Foreign Ministry compared the Croatian measures to the racial laws enforced by its World War Two-era Nazi puppet regime.

“In their discriminatory character, they can only be compared with measures taken in the past, during the fascist Independent Croatia,” the ministry said in a statement.

Almost 50,000 migrants have flowed into European Union-member Croatia via Serbia in little over a week since Hungary, northern neighbor to both countries, barred their entry to the EU by sealing its border with Serbia with a metal fence.

Zagreb says Serbia should send them to Hungary and Romania too, and last week closed seven of eight border crossings with Serbia to vehicles before halting cargo traffic altogether in an attempt to exert pressure on Belgrade.

As a midnight deadline set by Serbia for Croatia to lift the blockade expired, Belgrade announced it was banning entry to all Croatian cargo vehicles and Croatian-made goods.

Croatia swiftly replied, halting all Serbian-registered vehicles. Serbian passport holders were also being turned back at the border, Reuters witnesses said.

Police gave conflicting information, but Croatian Interior Minister Ranko Ostojic said: “As far as people are concerned, they can enter Croatia.” On Twitter, the Croatian government later said the vehicle ban applied to Serbian cars entering from Serbia, but not necessarily from Croatia’s other neighbors, such as Bosnia.

The row risks setting back years of work in rebuilding relations between Serbia and Croatia since the overthrow of Milosevic, who backed ethnic Serb forces in Croatia and Bosnia with guns, men and money during the collapse of the Yugoslav federation in the 1990s.

Serbian Justice Minister Nikola Selakovic said Serbia had been “brutally attacked by Croatia.”

Croatian Prime Minister Zoran Milanovic, whose center-left cabinet faces a fight for power with conservative opponents in a parliamentary election this year, said he would not allow Serbia “to make fools out of us”.

“Citizens of Serbia, all your prime minister needs to do is to stop such an intense flow of migrants,” he said in Zagreb on returning from an EU summit on the migrant crisis in Brussels. “We can function with 4,000 to 5,000 people a day. But more than that will not work, and I will not allow it.”