Five drones were spotted flying over Belgium’s Doel nuclear power plant near the Port of Antwerp on Sunday evening, energy company Engie said.

“Initially we had detected three drones, but then we saw five drones. They were up in the air for about an hour,” Engie spokesperson Hellen Smeets told POLITICO Monday morning.

The first report of the three drones came shortly before 10 p.m. on Sunday, Smeet said, adding that the sightings had no impact on the plant operations. Belgium’s national Crisis Center, which is currently monitoring the situation, confirmed the incident.

Earlier in the evening, air traffic at Liège Airport was briefly suspended after multiple drone reports, with flights halted around 7:30 p.m. and resuming less than an hour later.

The latest incidents comes amid a surge of drone activity disrupting key infrastructure across Belgium. Airports in Brussels and Liège faced repeated interruptions last week, while drones were also spotted over military bases and the Port of Antwerp.

Belgium held a National Security Council meeting Thursday, after which Interior Minister Bernard Quintin said that authorities had the situation “under control.”

While the government has avoided attributing blame, Belgium’s intelligence services suspect foreign hands, with Moscow seen as the most likely source, according to local media. Defense Minister Theo Francken said Saturday that “Russia is clearly a plausible suspect.”

On Sunday, the U.K. announced it will join France and Germany in sending personnel and equipment to help Belgium counter drone incursions around sensitive sites.