Romanian President Nicușor Dan has declared the Russian consul in Constanta persona non grata and said the Russian consulate in the Black Sea port city would be closed.
Romania on Friday said a Russian drone carrying explosives crashed in the eastern city of Galați, causing a fire on the roof of a residential apartment block.
The building was evacuated and two people were injured, Oana Toiu, Romania's foreign minister, said.
"Two aircraft and a helicopter belonging to the Romanian Air Force were scrambled when Russian drones appeared on the radar, they had permission to shoot," Toiu said in a statement posted to social media, adding that it was "a serious and irresponsible escalation" by Moscow.
Romanian defence minister Radu Miruță identified the drone as a Geran-2, the Russian version of the Iranian-designed Shahed-136 drone, Euronews Romania reports.
It was detected by radars and flew in Romanian airspace for around four minutes, Miruță said, adding that the explosives on board the drone detonated when it hit the building. Authorities are now working to recover debris from the crash.
An investigation is currently ongoing at the scene, and the perimeter has been secured, although residents have not yet been allowed to return home.
Euronews Romania reports that the two injured people are a 53-year-old woman and her 14-year-old son. They were taken to hospital for treatment for burns and are in a stable condition.
Romanian President Nicușor Dan has since declared the Russian consul in Constanta persona non grata and said the Russian consulate in the Black Sea port city would be closed.
Romania has also summoned the Russian ambassador to the headquarters of the Ministry of Foreign Affairs regarding the incident.
NATO and Europe react
The incident has sparked strong criticism from leaders across Europe.
EU Commission President Ursula von der Leyen said on Friday that Russia had "crossed yet another line" and vowed to continue to put pressure on Moscow.
"We stand in full solidarity with Romania and its people," von der Leyen said, adding that the EU was prepping a 21st package of Russian sanctions.
In a statement, NATO condemned Russia’s "recklessness" and said the alliance would strengthen its defences against "all threats, including drones".
Ukrainian President Volodymyr Zelenskyy called for strong sanctions against Moscow and said the stray drone had been part of a Russian attack on Ukraine's southern Odesa region, which borders Romania.
NATO's eastern flank has been plagued by errant drone incursions in recent weeks, with a wave of incidents taking place across Estonia, Latvia and Lithuania.
Moscow has accused the Baltic states of allowing Ukraine to use their airspace to carry out attacks on Russian soil and threatened to take action against them.
The Baltic governments issued a joint statement alongside Nordic allies saying they "firmly reject Russia’s blatant disinformation campaign and false claims".
"The Nordic-Baltic countries have never allowed their territory or airspace to be used for these attacks against targets in Russia," the statement read.
Speaking to Euronews earlier this month, Robertas Kaunas, Lithuania's minister of defence, said the Baltics must be prepared for even more drone incursions.
“This is the new reality of what the Baltic states face,” he told the Europe Today news programme. “We need to adapt because the possibility of repeated similar scenarios is very high.”