Persistent attacks in the escalating maritime war between Russia and Ukraine are creating a major challenge for NATO in the Black Sea, leaving member states Romania and Bulgaria exposed.
After seven strikes on cargo ships near them, the alliance announced plans to deploy maritime patrol aircraft, drones and radar to bolster its eastern Black Sea flank.
Three days later, on Oct. 23, another ship was attacked just outside Romanian waters. Last week, naval drones sank a Greek container ship in Bulgaria's exclusive economic zone.
Military analysts had little doubt these were Russian attacks. A naval drone in video of the last strike resembled a Russian variant, said shipping security firm Ambrey.
"I think it's undeniably an escalation," said Sidharth Kaushal, a senior fellow at the London-based RUSI think tank.
Russia denies targeting Ukraine's neighbors with drones and says European governments escalate the war in Ukraine by supplying military aid. Russia's Defense Ministry did not respond to a request for comment.
Russia testing red lines
Many of the ships hit in October were near or sailing to or from a key Romanian canal used by Ukraine for exports. One was in Romanian territorial waters; eight others were in its or Bulgaria's exclusive economic zone.
Iulia Joja, director of the Black Sea program for the Washington-based Middle East Institute think tank, said Russia's attacks took into account the West's aversion to escalation.
"This is about testing these red lines, with full awareness that we will do everything possible to take the most minimal measures," Joja said, drawing a comparison with Russian drone incursions into NATO airspace in recent years.
A NATO official said Russian actions aimed at dissuading the allies from supporting Ukraine pose a serious security threat and the bloc's commitment to defending all its members, including those on the Black Sea, is "ironclad."
The official said there is a clear need for cost-effective counterdrone capabilities, but the alliance already committed to investing more than $40 billion in counterdrone capabilities over the next five years.
Crucial waterway
For Romania, the Black Sea is a crucial waterway for trade and home to its offshore Neptun Deep project, which will make it the European Union's largest gas producer next year. A naval drone approached Neptun Deep in August.
Bucharest has accused Russia of "systematic" strikes on civilian ships but has not attributed individual attacks, citing the need for forensic evidence. Sofia has not blamed Russia, but said some attacks appear to benefit it.
The strikes occur as Washington reassesses its military presence in Europe to focus on China. The U.S. withdrew 1,000 troops from Romania last year.
"It's a moment in the transatlantic relationship that Putin likely wants to use," a senior Romanian official said. "The EU and NATO's attention is important, and their forces currently focus on the north and the Baltics."
While NATO has reinforced its "enhanced forward presence" for the Baltics and Poland, Joja said it has not done the same in Romania despite Bucharest's requests.
"Brussels and Washington still have not decided whether the Black Sea is fully part of the NATO commitment," he added.
The Romanian official stressed Romania's pressing need for surface-to-air interceptors and radar systems to counter threats.
Joja said the limited availability of cheap interceptor weapons, exacerbated by the war in Ukraine, is a central problem for the West.
The surge in strikes on Black Sea shipping has strangled a major conduit for Russian and Ukrainian grain and oil exports.
The two sides hit 317 merchant and other vessels in the Black Sea and Sea of Azov between May and October, more than quadrupling the 74 vessels hit in the previous half-year, according to Tomas Alexa, a senior analyst at Ambrey.
The tempo of attacks has fluctuated ahead of the second anniversary of Russia's full-scale invasion in February. Ukraine carried out 137 attacks on ships compared with 92 Russian attacks in the third quarter, while in October, Russia hit 38 compared with five Ukrainian attacks, Ambrey said.
Grain exports slump
Ports have been damaged, and exports have shrunk, forcing Russia and Ukraine to seek alternative export routes.
Russia exported only 300,000 metric tons of grain in September through the Black Sea and Sea of Azov, down from 4.74 million metric tons in September last year, according to Russian export data reviewed by Reuters.
Ukraine suspended Black Sea port operations in late July due to Russian attacks, prompting it to divert volumes to river ports on the Danube and through Romania's Sulina Canal and its Black Sea section.
Even with this alternative route, Ukraine's port grain exports slumped to 810,000 metric tons in September compared with 2.1 million metric tons in September last year, government data show.
Andriy Ryzhenko, a naval analyst and former senior Ukrainian naval officer, said Russia's primary goal is further reducing these volumes, with testing NATO as a secondary objective.
Food crisis warning
Last week's attack occurred as the defense ministers and military chiefs of Romania, Bulgaria and fellow NATO member Türkiye met in Sofia to discuss the situation.
Türkiye's defense minister, whose country awaits responses from Moscow and Kyiv on a narrow maritime cease-fire proposal, used the meeting to warn Russia and Ukraine against further attacks.
Ankara controls the transit of warships through the Bosporus and Dardanelles under the Montreux Convention.
Several countries, including Egypt, Türkiye and India, pushed for maritime cease-fires to avert fallout from shipping disruption as global fuel and grain prices soared.
U.S. Secretary of State Marco Rubio said Saturday there was growing international interest in a limited cease-fire.
Russia has rejected the idea of a narrow maritime cease-fire, saying it would provide Kyiv respite. Ukrainian President Volodymyr Zelenskyy has sounded the alarm.
"Everyone is talking about diesel and forgetting about grain. In a month or two, everyone will start talking about an agricultural crisis," he said last month.