Rheinmetall's chief executive says he will not step back after threats, as a drone explodes beside a gas pipeline in Bulgaria

Armin Papperger, chief executive of the German arms manufacturer Rheinmetall, said on Sunday that he will not withdraw from his role despite continuing threats to his safety that keep him under permanent protection. German authorities have previously linked plots against him to Russia. Moscow has denied involvement in such plots.

A separate incident on Saturday showed how such threats can become physical, several hundred kilometres to the south east. A drone crossed from Romania into Bulgarian airspace and exploded about 1,000 metres from a compressor station on the Trans-Balkan gas pipeline, near the Kardam border crossing. It carried a significant quantity of explosives and caused no casualties. Bulgaria's defence ministry said debris analysis showed a type widely used by the Ukrainian military, while adding that nothing currently suggests the incident was deliberate. Ukraine's foreign ministry said its armed forces did not intentionally direct any assets toward Bulgaria and promised an explanation.

Turkish officials separately said a drone attack the previous day on two civilian vessels in the Black Sea injured crew members. The Trans-Balkan line connects Turkey to Ukraine and now carries gas in the reverse of its original direction.

Two costs are accumulating for European industry. Defence manufacturers are paying for executive protection, plant security and vetting on a scale they did not budget for, and pipeline operators, ports and grid managers across the Black Sea rim are paying for surveillance and hardened defences against a threat that arrives from the air and cannot be attributed with confidence.