Ukraine said today that Russian drones crashed and exploded on the territory of NATO member Romania. during an overnight attack on Ukrainian port infrastructure on the Danube River, but Bucharest categorically denied the information.

Reuters could not independently verify either version of what could have been a dramatic turn in Russia’s war against Ukraine that began 18 months ago. Moscow regularly carries out long-range airstrikes against targets in Ukraine, which borders Romania.

“According to the State Border Guard Service of Ukraine, yesterday, Sunday evening, during a massive Russian attack near the port of Ismail, Russian [drones] “Shakhed” fell and exploded on the territory of Romania,” Ukrainian Foreign Ministry representative Oleg Nikolenko wrote on Facebook.

“It is another confirmation that Russian missile terror is a huge threat not only to the security of Ukraine, but also to the security of neighboring states, including NATO member countries,” he said.

Romania’s Ministry of Defense issued a statement saying it “categorically” denies the Ukrainian claims.

NATO has a collective defense commitment based on which the military alliance considers an attack on one ally to be an attack on all allies.

Nikolenko released a photo showing flames from an explosion on the opposite bank of the Danube Riverthe dividing line between the Ukrainian region of Odessa and the Romanian territory.

A Ukrainian industry source told Reuters that two Russian drones fell on the Romanian side.

The Ukrainian president’s chief of staff said that the incident shows the need to increase the supply of modern anti-aircraft and long-range weapons so that Russia does not have the ability to launch drones and missiles like Ukraine.

“Additional weapons and long-range missiles for Ukraine — to accelerate the liberation of our territories from occupation. Russia must be defeated on the battlefield,” the official, Andriy Yermak, said on the Telegram app.

Ukraine’s ports of Reni and Ismail on the Danube accounted for about a quarter of Ukraine’s grain exports before Russia pulled out of a deal which was achieved with the mediation of the UN and ensured the safe passage of Ukrainian grain exports through the Black Sea.

Since then ports on the Danube have become the main exit route from Ukraine, with grain also sent by barge to the Romanian port of Constanta on the Black Sea for onward shipment.

The overnight attack on Ukrainian port infrastructure took place just hours before scheduled talks between Russian President Vladimir Putin and Turkish President Tayyip Erdogan.