Bulgaria will move migrants who clashed with police at a refugee camp to closed camps and hopes to start extraditing some of them to their native Afghanistan next month, Prime Minister Boiko Borisov said on Friday.

More than 400 asylum seekers, angered at being confined at the camp in the southern town of Harmanli near the border with Turkey over a health scare, were arrested after clashes with riot police late on Thursday. The police used water cannon and rubber bullets to quell the riot, in which the interior ministry said 24 officers were hurt. Three migrants sought medical help after the riot, it added. On Friday morning the refugee camp, Bulgaria's largest and home to some 3,000 asylum seekers, looked like a war zone, with broken windows, overturned trash containers and debris. "I am very worried ... You see there is no window left unbroken. The people who committed these acts of vandalism will be brought to justice," said Borisov, who cancelled a planned visit to Hungary because of the riot.

More than a million migrants and refugees have entered the European Union over the 15 months, many fleeing conflicts in Afghanistan, Syria and Iraq. Some have entered Bulgaria, an EU member, from Turkey hoping to carry on to wealthy Western Europe where most want to settle and build a new life. Borisov urged residents of Harmanli to stay calm and to avoid provoking the asylum seekers. A small group of local people waving national flags demanded the camp's closure. Last week some local people, led by nationalist parties, staged protests against the camp following media reports that migrants were suffering from contagious skin diseases. The tensions caused the temporary closure of the camp to allow health officials to investigate. They said the reports had been exaggerated and that there was no public health risk. Bulgaria has built a fence along its border with Turkey and has beefed up border controls to deter the migrants. Some 17,000 people were detained in the first 10 months of the year, down by more than a third from the same period in 2015.