Croatia is banning Serbians and cars from Serbia from entering the country one day after Serbia banned Croatian cargo vehicles and goods from crossing its border.
The ban, announced by Croatia on September 24, is the latest in a border dispute between the two countries over the flow of migrants streaming into the Balkan countries on their way towards wealthier Northern European countries.
Serbia first retaliated after Croatia closed all of its border crossings with Serbia except one nearly a week ago.
Only hours before moving against Croatia, the border spat had seemed to be cooling as the two sides allowed truck traffic to briefly flow through the main border crossing at Bajakovo after a two-day blockade imposed by Croatia.
Croatia has said it will not lift the blockade on most border crossings until Serbia starts redirecting migrant traffic back into Hungary. However, Hungary has largely sealed its border with Serbia and is now moving to close its border with Croatia as thousands of migrants have been trying to cross there.
More than 51,000 refugees have arrived in Croatia since Hungary sealed off its border with Serbia eight days ago.