Sailors from the sunken merchant vessel HS Dignity are brought to safety in the port of Varna, Bulgaria, following a drone strike on their ship on Tuesday Emily covers breaking news from all over the world. She previously reported on home news and politics for The Telegraph. You can reach her at emily.smith@telegraph.co.uk 4:55pm BST The Royad Mammadov was carrying a full cargo of Ukrainian corn across the Black Sea, bound for the Italian port of Ravenna, when two drones struck.

A fire broke out on board and within hours of the attack, the 139-metre Turkish-owned vessel was at the centre of a rescue operation near the fishing port of Sfântu Gheorghe, off Romania’s coast.

Eleven Azerbaijani and Indian nationals were rescued but two bodies were recovered from the sea, including the ship’s captain.

Volodymyr Zelensky blamed Russia for what he called a “horrific strike” on a civilian vessel in neutral waters.

Rumen Radev, Bulgaria’s prime minister, told his country’s parliament “there is no logic in Ukraine attacking its own ships and crews, given that the outcome of all these attacks favours Russia – and indeed, the logic points in that direction.”“The problem is that we cannot prove it.”Two crew members were killed when the Royad Mammadov, carrying a full cargo of Ukrainian corn to Italy, was struck by a drone off the Romanian coast on Oct 5 The drone attack, on Oct 5, is one of at least eight on cargo vessels in the western Black Sea in the past month, bringing Russia’s war closer to the coastline of two Nato members, Romania and Bulgaria.

The attacks have raised fears about the spillover of the Russia-Ukraine war into Black Sea shipping lanes vital to Ukraine’s grain exports.

The strikes appear to be part of Moscow’s strategy to test Nato’s resolve, unsettle its eastern members and put pressure on Western governments to reconsider their support for Kyiv, while avoiding a direct military confrontation with the alliance.

Analysts told The Telegraph that the drone attacks in the two countries’ exclusive economic zones marked a “dangerous new direction for Russian actions”, and were a move taken from Iran’s playbook in the Strait of Hormuz, where cargo vessels have been repeatedly struck by drones.

On Tuesday, two more ships, the Chelsea 3, a Maltese-flagged but Ukrainian operated vessel, and the Guinea-Bissau-flagged HS Dignity were hit by drones off Bulgaria’s coast.

All 15 crew members aboard the Chelsea 3 were evacuated, while 11 sailors from the HS Dignity were reported missing.

The following day, the Yara J, a chemical and oil tanker sailing from Turkey to Romania was struck and caught fire.

On Thursday, the Wine Trader, a San-Marino-flagged chemical tanker travelling from Tunisia to Romania, was also hit and set ablaze. The search continued on Friday for seven sailors missing from the vessel.

October’s Black Sea drone incidents are just the latest in a lengthy series of airspace incursions that have rocked Romania and other NATO members since Moscow launched its full-scale invasion of Ukraine.

But Prof Andrew Mumford, professor of war studies at the University of Nottingham, said the recent strikes “do seem like a dangerous new direction for Russian actions”.

“They are still part of the Kremlin’s hybrid threat playbook,” he added. “They are determined to undermine Western interests, test NATO’s collective resolve, whilst keeping actions below a threshold of legitimate response,” he said. The strikes took place in Romania and Bulgaria’s exclusive economic zones, rather than their territorial waters.

And although the countries have rights over resources in these zones, they do not exercise full sovereignty over them, leaving a grey area as to whether Nato’s Article 5 – defining an attack on one member as an attack on all – would be triggered.

Dr Rod Thornton, Russian defence expert at King’s College London, said the attacks exploited this uncertainty.

“These strikes are risk free for Russia because these vessels being hit are not registered. They’re flag of convenience vessels, crewed by people who are basically from the developing world,” he said.

“You’re not going to kill any Western nationals by doing this. So it’s a kind of very convenient way of upping the ante by putting pressure on Romania and Bulgaria without kind of tipping over into NATO taking violent action against Russia.

The tactic echoes that used by Iran in the Strait of Hormuz to exert economic and political pressure through attacks on commercial shipping“You can’t tell exactly where the strikes came from. So there’s always going to be this grey area, plausible deniability about these attacks.”Dr Thornton said that Moscow had previously been reluctant to risk provoking Nato by striking in the Black Sea, but that mounting pressure from Ukraine may have convinced Vladimir Putin of a need to raise the stakes.

“If one state like Iran is probably quite effective in its drone activity in the Strait of the Hormuz, then it makes kind of perfect sense for the Russians to try and copy that,” he added.

Dr Shane O’Rourke, an expert in Russian history at the University of York, said the attacks reflected the Kremlin’s difficulties on the battlefield, with Ukrainian forces fighting Russia to a stalemate and striking targets deep behind the front line.

“Russia is having such a hard time on the battlefield that the Ukrainians not only have brought any Russian advances to a halt, but the Ukrainians themselves seem to be advancing,” he added.

The strikes appear to be part of Vladimir Putin’s strategy to test Nato’s resolve, unsettle its eastern members and put pressure on Western governments to reconsider their support for Kyiv“Operation Vivaldi appears to have been extremely successful and has inflicted a lot of damage on the Russians, and of course the continued strikes on Russian refineries, on the data centers, are having a real impact in Russia.

“So I think what we’re seeing now is a reflection of the fact that the war clearly isn’t going the way the Russians want it to go.”The attacks could also carry an economic cost beyond the immediate damage to ships and their crews.

Ukraine relies on Black Sea routes to export grain, while Romania’s port of Constanta has become an important hub for regional trade.

The Ukranian-operated Chelsea 3 was struck by a drone off Bulgaria on Tuesday Cezar Gheorghe, founder of grain consultancy firm Agricolumn, told the AP that the drone incidents have not negatively impacted trade at Romania’s Black Sea port of Constanta. The main concern is a rise in insurance costs in the wider Black Sea, he said.

“The (premium) for the risk is increasing, ... everyone that wants to come to Constanta, let’s say from Turkey, from the Bosphorus Strait and across that area, will have a (premium) on insurance costs,” he said.

He added his main concern is a “serious incident” occurring at or near Constanta. In June, a Ukrainian maritime drone exploded at the port, and three others nearby.