The city of Brussels was plunged into darkness Thursday due to a massive power outage.

The sounds of sirens were reported throughout the Belgian capital, which was the site of a coordinated terror attack last year that killed 32 civilians and injured hundreds more.

Videos and photos posted on social media showed the eerie scene.

“Power out as far as I can see in all directions,” tweeted Independent correspondent Jennifer Baker.

While the cause of the outage was initially not known, a spokesperson for Brussels’ power supplier, Sibelga, later told The Sun that the blackout was the result of an electric network distribution problem.

The Daily Mirror reported that Belgian security forces were boosting their manpower at main sites around Brussels as authorities assessed the situation.

The Belgian city is the site of several key EU bodies, including the European Commission and European Council.

The northern part of Brussels was said to have been affected the worst by the blackout, which was first reported at around 10:45 p.m. local time, according to the Daily Mail.

An earlier power outage reportedly struck a portion of city several hours earlier, but was resolved by 8:30pm, the outlet reports.