Bulgarian President Rumen Radev invited Russian President Vladimir Putin to visit Bulgaria in 2018 and to attend the celebrations of the country's 140th anniversary of liberation from the Ottoman rule, Radev's office said in a statement.

On June 9, Radev said that he was planning to invite the Russian leader to the celebrations.

"In light of the 140th anniversary of the end of the Russian-Turkish war of 1877-1878 and of Bulgaria's liberation, the head of state invited his colleague to pay an official visit to the country in 2018," the statement said on Monday.

The statement added that Putin thanked Radev for the invitation and accepted it, however, no specific date had been set yet.

The principality of Bulgaria was declared following the Russian-Turkish war in 1878, however, it was a nominal vassal of the Ottoman Empire until 1908.