NATO warplanes on Sunday shot down a drone that entered Romanian airspace and appeared to be Russian in origin, the second downing of a drone in alliance airspace in three days.

The downings are a fresh sign of spillover from Russia's invasion of Ukraine. Sunday's downing was the fourth over Romania since the war began in 2022.

NATO scrambled four jet fighters to shoot down a foreign drone that entered Latvian airspace early Friday. Latvia's Ministry of Defense didn't immediately identify that drone's origin but said it had entered the country's airspace "as a result of Russian electromagnetic warfare."

Romania detected an incursion from neighboring Moldova early Sunday morning local time, and NATO forces based in Romania scrambled two Spanish air force F-18s on rotation to the region. One of the jets shot down the drone over an unpopulated area in the country's east, Romania said.

The incident is under investigation, "but the drone appears to be Russian," said U.S. Army Col. Martin O'Donnell, spokesman for the North Atlantic Treaty Organization's military command. It is rare for the alliance to point a finger at Moscow so quickly.

Drone incursions into NATO airspace have become a near-weekly occurrence this summer. Many are believed to result from Russian or Ukrainian electronic-warfare systems interfering with drone navigation equipment, but some are also suspected of being Russian attempts to probe NATO air defenses. The incursions add to anxiety among alliance members about the potential for Russia to test the alliance's resolve with direct or indirect aerial intrusions.

Intercepting a drone with two advanced jet fighters is extremely expensive. O'Donnell said that NATO, Romania and other allies are acquiring ground-based interceptors to boost air-defense capabilities.

NATO has a large presence at Romania's Mihail Kog lniceanu Air Base.