NATO member Romania said that a drone injured two people in a southeastern city during an overnight Russian attack on neighboring Ukraine, the first time in the conflict that a drone has hit a densely populated area in Romania and caused injuries.

The incident in Romania, also a member of the European Union, was likely to increase tensions on NATO's eastern flank at a time when Ukraine's allies are worried about Russia's campaign in Ukraine spilling over its borders.

"We condemn Russia's recklessness, and NATO will continue to strengthen our defenses against all threats, including drones," a NATO spokesperson posted on X.

The drone hit the roof of a 10-story block of flats in Galati and caused an explosion, the Romanian authorities said.

"Initial information indicates that the entire load of the Geran 2 drone, of Russian origin, exploded upon impact," the defense ministry said in a statement.

'Serious violation'

Romania, which shares a 650km land border with Ukraine, has experienced Russian drones breaching its airspace 28 times since Moscow began attacking Kyiv's ports across the Danube River, Romania's defense ministry said.

Romanian Foreign Minister Oana Toiu called the incident a "serious violation of international law" and said that Bucharest had "requested measures to accelerate the transfer of anti-drone capabilities to Romania." 

She said the Russian ambassador had been summoned to the foreign ministry.

European Commission head Ursula von der Leyen said Russia had "crossed yet another line."

There was no immediate comment from the Russian defense ministry.

Ukrainian drones have strayed into Baltic countries' airspace in recent weeks, sowing confusion and raising tensions with Russia.

The Romanian defense ministry said it scrambled two F-16 fighter jets and a military helicopter to monitor the attack, adding the pilots were authorized to shoot down any drones. The residents of border counties Braila, Galati and Tulcea were warned to take cover.

Romanian Brigadier General Gheorghe Maxim told a press conference that the drone was in Romania's airspace for four minutes, flying low, making it difficult for radar to detect. He said the US anti-drone system Merops was operational in Romania but would have been too risky to use in a city.

In Friday's incident, a fire broke out in a 10th-floor apartment after the drone struck the building's roof and exploded, Romania's emergency response agency said. Two people were receiving medical treatment on site, it said, adding 70 people had evacuated.

State news agency Agerpres cited Galati's emergency response agency as saying a woman and her child had been taken to hospital with minor injuries while two others had been treated on site for panic attacks.

'Strategic task'

Deputy Interior Minister Raed Arafat, who is in charge of the emergency response agency, told private broadcaster Digi24 the drone affected two building stairwells and damaged five cars.

A drone incursion into Romania during a Russian attack on Ukraine proves that Moscow's aggression poses a threat to the Black Sea region and the wider European continent, Ukrainian Foreign Minister Andrii Sybiha said.

"Ukraine stands firmly by Romania. We are ready to work closely together to strengthen protection from such threats," Sybiha said on X.

He added that strengthening Ukraine's air defense was a "strategic task" to protect not only Ukraine but also to reduce risks for neighboring countries.

Romanian President Nicusor Dan said: "The unprecedented nature of the event demands a firm, coordinated and proportionate response - at national, allied and international level."

Meanwhile, Nato Secretary General Mark Rutte vowed to "defend every inch of Allied territory."

EU Foreign Policy Chief Kaja Kallas called the Russian drone crashing into apartments a "serious violation of Romania's sovereignty and European airspace."

And Hungarian Deputy Prime Minister Anita Orban said that the attack "underlines that Europe and NATO's unity, strength and deterrence are more important than ever."

In a separate incident, a drone without an explosive charge was found around Basesti in Maramures county in northwestern Romania and the area was secured, state TVR broadcaster said late on Thursday, citing local authorities.

The authorities were investigating the origin of the drone, which the report said had a wingspan of about three meters, and how it happened to be in the area, TVR added.

Local authorities in southern Ukraine, meanwhile, said the Izmail port in the Odesa region came under attack from several drones early on Friday.

Izmail, close to the Romanian border, is home to the largest Ukrainian port on the Danube River and is a frequently targeted strategic location.

Galati was last hit in April, when a drone damaged an electricity pole and a household annex, prompting evacuations. Officials retrieved that drone to detonate its unexploded payload remotely.