The Belgian energy company Engie reported that five drones were spotted flying over the Doel nuclear power plant near the port of Antwerp on Sunday evening.
"Initially, we detected three drones, but later we observed five. They were airborne for about an hour," said Engie spokesperson Hellen Smeets to POLITICO.
She noted that the first report of the three drones came in around 10 PM on Sunday, adding that the drones did not disrupt the plant's operations. The Belgian National Crisis Center, which is monitoring the situation, confirmed the incident.
Earlier that evening, air traffic at Liège airport was halted due to multiple reports of drones; flights were suspended around 7:30 PM and resumed in less than an hour.
Brussels and Liège airports had faced disruptions last week as well, with drones also sighted over military bases and the port of Antwerp.
On Thursday, a National Security Council meeting took place in Belgium, after which Interior Minister Bernard Quatennens stated that the authorities are "keeping the situation under control".
While the government has refrained from making assumptions about the drones' ownership, Belgian intelligence suspects foreign involvement, with Moscow considered the most likely source. Defense Minister Theo Francken identified Russia as "certainly the most obvious suspect".
On Sunday, the United Kingdom announced its intention to join France and Germany in sending personnel and equipment to assist Belgium in countering drone incursions around sensitive sites.