By Natalia Zinets
KIEV (Reuters) - Ukraine said on Thursday it was checking reports that Bulgaria's Eurovision song contest entrant, one of the favorites to win, may have broken Ukrainian law by performing in Crimea after its annexation by Russia.
A video widely shared on social networks and in Ukrainian media appears to show Bulgarian Kristian Kostov singing at a concert on Ukraine's Black Sea peninsula in June 2014, three months after it was seized by Russia.
Ukraine has already barred Russia's contestant from entering the country because she had performed in Crimea.
Forty-two countries are competing this year in Eurovision, an annual pageant of the colorful, the camp and the cheesy that in recent years has increasingly been drawn into politics. Ukraine's Jamala won last year with a song about war-time deportations of Crimean Tatars by Soviet dictator Josef Stalin.
Kostov, who at 17 is the youngest competitor this year, is due to take part in the second semi-final on Thursday with his song 'Beautiful Mess.' The final takes place in Kiev on Saturday in front of a television audience of millions.
Ukraine's border service said it and other state security agencies had not known about any visit by Kostov to Crimea when he entered Ukraine to take part in the competition. "We will study the information," spokesman Oleh Slobodyan said.
Slobodyan said Kostov may not have broken Ukrainian law if he visited Crimea as a minor and before legislation came into force banning foreigners from visiting the annexed territory without permission from Ukrainian authorities.
In a statement, the Bulgarian Eurovision delegation confirmed that Kostov had visited Crimea "for just a few hours" when he was 14 years old as part of a children's musical group.
There was no immediate comment from Eurovision organizers.
The annexation of Crimea contributed to a collapse in relations between Russia and Ukraine in 2014.
Russian singer Dima Bilan, who won Eurovision in 2008, urged his 1.9 million Instagram followers on Thursday to vote for Kostov. "He represents Bulgaria, but he is our hero!" he said in a post.
(Reporting by Natalia Zinets; Additional reporting by Margaryta Chornokondratenko; Tsvetelia Tsolova in Sofia; Writing by Alessandra Prentice; Editing by Mark Trevelyan)