Il Nuovo Postiglione - Drone enters Bulgaria, explodes near pipeline at Romanian border

While Radev did not specify where the drone, which caused no casualties, came from, he 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.

After analysing the debris from the crash, Bulgaria's defence ministry said that the drone was of a type "widely used by the Ukrainian military".

It said that, "currently, nothing suggests that this was a deliberate incident".

The drone eventually crashed into a sunflower field, Radev 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.

"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.

- Boosted surveillance -

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 full-scale invasion of Ukraine in 2022, ordered the expulsion of a Russian embassy staff member in late July.

Radev said that, following the latest incident, Bulgaria has boosted its surveillance and will redeploy troops and soldiers to the borders to detect drones and employ anti-drone measures.

Bulgaria, Romania and Turkey all front onto the Black Sea, which is an arena of drone combat by both Ukraine and Russia.

Turkish officials on Tuesday said a drone attack the previous day on two civilian vessels in the Black Sea left crew members injured. Turkey's foreign ministry said it was "deeply concerned about the escalating conflict" in the body of water.

Bulgaria in June halted its military aid to Ukraine, with Radev saying that the country did not belong in the coalition of Kyiv's allies that are supplying arms and preferred to see diplomatic efforts to end the war.

D.Ricci--INP