Crimea: Video shows alleged Russian ship ram Ukrainian tugboat in Black Sea as tensions rise

Naval clashes near Kerch Strait prompt Petro Poroshenko to propose martial law

Footage has emerged showing an alleged Russian ship ramming a Ukrainian tugboat during a naval clash that has sparked fears of an international escalation of hostilities between the two sides.

The video shows the tugboat being struck on its starboard by the much bigger ship near the hotly contested Kerch Strait, which separates the Crimean peninsula from the Russian mainland in the Black Sea.

Arsen Avakov, Ukraine's minister of internal affairs, tweeted the video the Ukrainians claim was filmed by the Russian side of the incident.

Russia’s coastguard opened fire and seized the three vessels – the tug and two gunboats, which were on their way from Odessa to Mariupol – after a tense standoff on Sunday, the Ukrainian navy said. Six Ukrainian crew members were reportedly wounded.

Russia blamed Ukraine for provoking the incident, saying the vessels had made an unauthorised passage through its waters.

Ukrainian authorities said they had given advance notice to the Russians that the vessels would be moving through the strait, which connects the Black Sea to the Sea of Azov.

Earlier in the day, Russia and Ukraine traded accusations over a separate incident involving the same vessels, prompting Moscow to block passage through the narrow Kerch Strait, which separates the peninsula from the Russian mainland.

The Ukrainian navy said its two gunboats were struck before Russian crews boarded and seized them and the tugboat.

Russia’s Federal Security Service, known as the FSB, which oversees the coastguard, said there was “irrefutable evidence that Kiev prepared and orchestrated provocations ... in the Black Sea”, adding: “These materials will soon be made public.”

The FSB confirmed early on Monday that it fired on the vessels to force them to stop, and then seized them.

The clash has sharply escalated tensions that have existed since Moscow annexed Crimea from Ukraine in 2014.

An emergency meeting of the United Nations Security Council was called for Monday morning over the escalating situation.

The European Union and NATO called for restraint from both sides and for Moscow to restore access to the strait, which Ukraine uses to move ships to and from ports on either side of the peninsula.

"Russian coastguard vessels ... carried out openly aggressive actions against Ukrainian navy ships,” the Ukrainian statement said, with the tugboat suffering damage to its engine, hull, side railing and a lifeboat.

The Kerch Strait is the only passage into the Sea of Azov. The strait is spanned by the recently completed Kerch Bridge, connecting Crimea to Russia. Transit under the bridge has been blocked by a tanker ship, and dozens of cargo ships awaiting passage are stuck.

Russia has not given any indication of how long it will block the strait, but a long-term closure would amount to an economic blockade of Ukrainian cities on the Azov coast. Russia’s Black Sea Fleet greatly outmatches the Ukrainian navy.

Ukrainian ports on the Sea of Azov include strategically vital centres such as Mariupol, the closest government-controlled city to Donetsk and Luhansk, the breakaway regions of eastern Ukraine controlled by Russia-backed separatists. Thousands of people in those regions have been killed in fighting between Ukrainian troops and the separatists since 2014.

Although a 2003 treaty designates the Kerch Strait and Sea of Azov as shared territorial waters, Russia has been asserting greater control over the passage since 2015.

The Ukrainian Foreign Ministry said earlier that Russia’s actions violated the UN Charter and international law, and pledged to “promptly inform our partners about Russia’s aggressive actions”.

“Such actions pose a threat to the security of all states in the Black Sea region,” the statement said, “and therefore require a clear response from the international community.”

Ukrainian president Petro Poroshenko, after a meeting with his National Security Council, said in a statement that he would ask parliament on Monday to take up the issue of whether to implement martial law over the incident.

Dozens of people gathered outside the Russian Embassy in Kiev to protest against Moscow’s actions.

Additional reporting by agencies