PP and Romania's Save Romania Union (USR) have asked NATO to strengthen its joint military operations centre and rotational command in the Black Sea countries. The letter to Secretary General Mark Rutte follows drone attacks on commercial ships, the PP press office said.

This report follows our earlier story on defence minister Dimitar Stoyanov's talks with his Romanian and Turkish counterparts after the overnight strikes on two commercial ships in the Black Sea on 13 October.

PP leader Asen Vassilev, USR leader Dominic Fritz, Romanian MEP Dan Barna and PP MEP Nikola Minchev signed the letter. Barna and Minchev belong to the Renew Europe group, whose president, Valérie Hayer, backs the letter.

The two parties also want an urgent review of extra defence steps: stronger maritime surveillance, the means to counter drones, and better air and missile defence. They say these steps should prepare Bulgaria, Romania and their allies for future threats.

Drones have hit commercial ships near the territorial waters of Bulgaria and Romania, and recently inside Romanian territorial waters. On 6 October, sea and air drones struck two ships in Bulgaria's exclusive economic zone in the Black Sea. A week later, on 13 October, drones attacked two ships again.

The authors call the events a serious escalation and a growing threat to the security of Europe and NATO's Eastern Flank, especially after the strikes in recent hours in Romanian territorial waters. "Europe's security starts at its borders," the letter says. It says the Black Sea must be recognised as one of Europe's most important security priorities.

PP says threats to collective security demand immediate and firm action when ships have been sunk, crew members are reported missing and civilians are at risk. The party believes the first evidence clearly points to Russian involvement.

Prime minister Rumen Radev spoke by phone on Wednesday with European Commission president Ursula von der Leyen and with Mark Rutte. He called for a joint effort to stop the attacks on commercial ships in the Black Sea.

The letter welcomes the fact that the European Council and the European Parliament will discuss the worsening security situation in the Black Sea.