BUCHAREST, Romania (AP) — The discovery of drone debris on Romanian territory this week has left some local residents fearing that the war in neighboring Ukraine could spread into their country, as Russian forces bombard Ukrainian ports just across the Danube River from NATO-member Romania.

Moscow aims to disrupt Ukraine’s ability to export grain to world markets with a sustained campaign of attacks targeting Ukrainian Danube ports, and has attacked the port of Izmail four times this week, Ukrainian officials say.

Across from Izmail, pieces apparently from a drone were found near the Romanian village of Plauru, Romanian Defense Minister Angel Tilvar said Wednesday. It was unclear if Romanian authorities had determined when or from where the drone was launched, and Tilvar said the debris didn’t pose a threat, but the development has left citizens in the European Union nation feeling uneasy.

Daniela Tanase, 46, who lives in Plauru with her husband and son, told The Associated Press that the drone strikes on Izmail this week have woken her up, and that villagers “are scared” of the persistent Russian attacks.

“In the first phase (of the war) things were calmer, but now it has come to our territory,” she said. But added: “For now, we haven’t thought of leaving the area — we hope it will pass.”

Tilvar visited Plauru and nearby areas Wednesday after confirming the drone findings to a local news channel, and Romania’s Defense Ministry said he told local authorities there would be additional measures to secure “the airspace at Romania’s borders.”

Romanian President Klaus Iohannis demanded an “urgent investigation.” If the debris were confirmed to have been from a Russian drone it would be an “inadmissable” violation of Romania’s sovereignty and territorial integrity, Iohannis said at the Three Seas Initiative summit in Bucharest this week.

Mircea Franc, the owner of a guesthouse in the area of Chilia Veche near Ukraine’s Kiliia port in the Danube Delta region, said he’s seen “fireballs” in the sky this week on the other side of the Danube River and that it has left villagers shaken.

“Last night … there were drones cruising on the other side of the river and the day before yesterday there were many, they are the first in our area since the war started,” he said on Thursday. “The atmosphere in the village is indeed one of panic ... and the fear is worst at night.”

Speaking at the EU parliament on Thursday, NATO Secretary-General Jens Stoltenberg said that the 31-nation alliance has been informed by Romania about the finding of drone pieces and that the episode “demonstrates the risks of incidents and accidents.”

“We don’t have any information indicating any intentional attack by Russia and we are awaiting the outcome of the ongoing investigation,” Stoltenberg said.

For Franc, the guesthouse owner, the close proximity of the war is already having a negative impact on his business since tourists are now “very reluctant to come here,” he said, adding that some local families have moved away from the area out of fear.

“We are worried because nobody can guarantee that (a drone) won’t fall on our side of the river,” he said. “For the last two nights, three-quarters of the village hasn’t been sleeping. Beyond trying to calm us down, the authorities can’t do much about it.”

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Stephen McGrath reported from Sighisoara, Romania. AP journalist Lorne Cook contributed from Brussels.