The Russian drone that officials say slammed into a Romanian apartment building on Friday morning, wounding two people on NATO territory, was not entirely unexpected.

For more than four years, residents of eastern Romania have lived with the near-constant threat of Russian attack drones, weapons of the war in neighboring Ukraine that have spilled over the border. Such drones, whether crossing intentionally or not, have often set off alarms; the incursion on Friday was the 28th officially recorded violation of Romania’s airspace since Russia’s February 2022 invasion of Ukraine, defense officials said, and the first to injure civilians.

Debris from Russian drones hitting targets in Ukraine has landed in Romania at least 47 times, officials say — often in residential areas.

“Such incidents demonstrate the Russian Federation’s lack of respect for the norms of international law and endanger not only the safety of Romanian citizens, but also the collective security of NATO,” Romania’s defense ministry said in a statement on Friday, hours after the drone hit the apartment building in the city of Galati, near the Danube River border with Ukraine.

The ministry called the drone incursions “a new challenge to regional security and stability in the Black Sea area.”

Crossing NATO borders

In the years since Russia’s full-scale invasion of Ukraine, drones have changed the nature of warfare, not just there but around the world. Now these cheap weapons are routinely intruding into NATO airspace, putting the military alliance and its border communities on edge — and testing Europe’s resolve to push back against Russia without sparking a wider conflict.

In response to the persistent incursions, NATO and the European Union are drafting plans for a coordinated “drone wall” along Europe’s eastern flank. But the relentless evolution of drone technology has left the alliance scrambling to modernize its air defenses and operating on constant alert.

In September, a NATO mission was created to defend the alliance’s territory from Finland to Turkey, after about 20 Russian drones flew into Polish airspace. Though the drones were shot down, the incursion was seen as a test of NATO’s defenses and its will to resist Russia.

Since then, according to a NATO military spokesman, Russian aircraft have been intercepted at least 300 times as of late April, including fighter jets that were escorted out of NATO territory. That figure does not include individual NATO countries’ responses to incoming drones and planes under their own authority.

The drone that hit the Romanian apartment building was a Geran-2, the defense ministry said — the Russian version of an Iranian one-way attack drone, the Shahed-136. Russia has used its model to overwhelm air defenses in Ukraine, a tactic that Iran has since mimicked against U.S. targets and allies in the Persian Gulf this spring.

Ukrainian drones also have recently fallen into NATO territory in Baltic states. Those incursions have stoked unease among some of Ukraine’s staunchest supporters, though officials in Ukraine and some of the Baltic states have blamed Russia for them, accusing it of diverting Ukrainian drones by interfering with their guidance systems.

“Defend every inch”

The strike in Romania on Friday could “justify” NATO to begin consultations about a possible response under Article 4 of the alliance’s treaty, Romania’s foreign minister, Oana Toiu, said in a televised interview. Article 4, signaling discussions at an urgent level, was invoked after a Russian drone swarm in Poland and incursions into Estonia by three Russian fighter jets in September.

“NATO stands ready to defend every inch of allied territory,” Mark Rutte, the NATO secretary general, said in a statement. “We will continue to enhance our readiness to deter and defend against any threat, including from drones.”

Ms. Toiu also said that her government had asked allies to speed deliveries of counterdrone systems to Romania, signaling a need for more air defenses.

Two Romanian F-16 fighter jets were scrambled to shoot down the Russian drone on Friday but ultimately held off, President Nicusor Dan said in a statement, “because the conditions did not exist to destroy it without the heightened risk of endangering civilian safety.”

At the very least, the incursion may lead to more caution among Romanians — and others on NATO’s eastern flank — who have become somewhat inured to constant alerts about incoming attack drones.

In Romania, many residents no longer bother to rush to bomb shelters or bunkers upon receiving Defense Ministry push alerts on their mobile phones, which have become frequent.

“I think everyone has already settled into a kind of normality with this situation,” Anca Vramulet, 40, said in a brief interview in April, just over a month before the Friday strike, while walking along the Danube with her 4-year-old son in the city of Tulcea, about 41 miles east of Galati. “If nothing has happened so far, we hope nothing will happen from now on either.”

Andrada Lautaru contributed reporting.