Ukraine has denied targeting Bulgaria after a drone exploded close to the strategic Trans-Balkan gas pipeline near the Romanian border.
Bulgaria's defence ministry said on Saturday the drone was of a type "widely used by the Ukrainian military", and the foreign minister summoned the Ukrainian ambassador for a meeting on Monday in response.
Kiev said it was "in close contact with the Bulgarian side to clarify the circumstances" of the incident.
"We can say with certainty that the Ukrainian Armed Forces did not intentionally direct any assets toward Bulgaria," Ukraine's foreign ministry spokesman Georgiy Tykhyi said.
While the explosion caused no casualties, Bulgarian Prime Minister Rumen Radev said the amount of explosives it was carrying was "significant".
"The drone exploded in the immediate vicinity of the Kardam border crossing with Romania," near the Black Sea in the country's northeast, "1,000 metres from the Trans-Balkan gas pipeline's compressor station," he said in a video released by the government on social media.
The drone later crashed into a sunflower field, he said.
The sound of the drone was recorded by border police in Romania, and then "a loud explosion accompanied by black smoke" was spotted by a Bulgarian border police patrol, Radev added, speaking after an extraordinary meeting of his cabinet's security council.
"One thing is certain: the drone was carrying a significant amount of explosives, given that it could be heard from a distance and produced such black smoke," he said.
The drone "crashed into a sunflower field, and I hope we will soon discover what type it is," Radev said, adding that it was not a "hobby drone" but a "larger drone".
He noted that the drone had not been detected by either of the two neighbouring countries.
"As you know, identifying and neutralising these drones poses a major challenge," he added.
Incidents involving drones have become increasingly frequent in recent months across Eastern European countries that are NATO members and supporters of Ukraine in its conflict with Russia.
Romania, which has faced frequent drone incursions — including some crashes on its territory — since the start of Russia's war on Ukraine in 2022, ordered the expulsion of a Russian embassy staff member in late July.
