molenbeek
A blackout hit Brussels late Thursday. Francois Lenoir/Reuters

UPDATE: 10:10 p.m. EST — Power officials tweeted the Brussels blackout was not the result of terrorism but rather a fault in the power grid.

Power was being gradually restored.

Original story

A blackout plunged large sections of Brussels into darkness Thursday and sparked fears of a terror attack. Sirens could be heard across the city.

The London Mirror said no cause for the outage had been given.

BNO News reported the blackout hit at 10:45 p.m., but it was not immediately clear how extensive it was although outages also were reported in suburban areas, including Etterbeek, Schaerbeek (also known as Schaarbeek), Saint-Josse, and Woluwe-Saint-Lambert.

Sibelga, which provides gas and electricity services, said a smaller outage that hit earlier in the day had been resolved by 8:30 p.m.

Brussels, which is host to a number of European Union agencies, has been hit by a series of terrorist attacks and was the hotbed of planning for the attack in Paris that killed 130 people and left hundreds more injured in November 2015.

The blackout sparked fears the darkness was either orchestrated by terrorists or would give them the perfect opportunity to strike. The Mirror said security personnel were reinforcing sites across the city.

Last year, three coordinated suicide bombings on March 22 killed 32 people and injured more than 300. The bombings occurred after a series of police raids targeting Islamic State group militants.

In May 2014, a gunman with ties to the Syrian civil war attacked the Jewish Museum of Belgium, killing four people. The following January, anti-terrorist authorities carried out operations against a group suspected of involvement in the Charlie Hebdo shootings in Paris that left a dozen dead. In August 2015, a suspected terrorist shot and stabbed passengers aboard a high-speed train headed to Paris from Amsterdam.

Suspects in the November 2015 attacks in Paris came from the Brussels enclave of Molenbeek.

Belgium is part of the military alliance fighting ISIS and was involved in the Iraqi civil war.