SOFIA (Reuters) - Bulgarian police on Tuesday arrested a Bulgarian man who had documented tying up three migrants near the Turkish border in a video posted on social media.
The prosecutor's office said it had opened an investigation into the case after the video went viral and drew criticism from human rights groups.
The video showed two men lying on the ground with their hands already tied behind their backs. A third man lay flat on his stomach as he was being restrained with long plastic cable ties, while an unidentified voice shouted in English: "Go back. Back Turkey. Now. No Bulgaria, go Turkey immediately".
A statement from the interior ministry said the incident had taken place in woods near the village of Zvezdets, some 5 km (3 miles) from the border with Turkey.
Bulgaria's Prime Minister Boiko Borisov initially praised the "boys" by declaring that protecting the country's borders was a joint effort.
However, following a backlash from human rights groups and local media who accused the prime minister of endorsing the actions of vigilante groups, Borisov made a U-turn.
"Society should not be indifferent ... but rights shouldn't be exceeded. Any illegal or inhumane attitude will not only not be tolerated but will also be prosecuted under the law," Borisov wrote in a Facebook post.
A number of vigilante groups have emerged in Bulgaria in recent months in response to Europe's migrant crisis. They include one set up by a Bulgarian trader in spare parts near the Turkish border which has won praise from some Bulgarians and raised serious concerns among others.
Last week a Sova Harris poll showed that 60 percent of Bulgarians think that refugees threaten national security.
The Black Sea state has stepped up security on its borders with Turkey and Greece to avoid a possible refugee influx.
Bulgarian border police say they have detained some 10,000 migrants from Syria and Afghanistan in the first three months of this year. Most migrants entering Bulgaria and other Balkan countries from Turkey or Greece aim to reach wealthier western Europe hoping to find jobs and better living conditions.
(Reporting by Tsvetelia Tsolova and Angel Krasimirov, Editing by Pritha Sarkar)