Maltese employees at EU institutions in Brussels were among a number of workers who stayed home yesterday as the city remained on lockdown following the “serious and imminent” threat of a Paris-style attack.

Schools, universities and child-care centres in the city were closed yesterday, with the tube network also remaining shut down, preventing a return to normal in the home of the EU’s main institutions.

Belgian police detained 21 people in 29 raids over the past two days, capping a tense day with hundreds of troops patrolling and authorities hunting for one or more suspected militants

Employees at the Council of the EU, where the threat level was raised to “orange” from “yellow”, were advised on Sunday night to stay at home if they felt uncomfortable travelling to work.

“I feel calm, as do most of the Maltese friends I spoke to this weekend, but it is hard for us to imagine how this lockdown can be prolonged for many more days,” said Elizabeth Galea, who works at the council.

Ms Galea was among those who stayed away from work yesterday and said colleagues who went to work informed her that the office was “very quiet”. Edward Demicoli, a media relations official at the European Commission, went to work as usual yesterday, although his wife stayed home to look after their child while schools remained closed, as did a number of his colleagues.

I feel calm. But it is hard for us to imagine how this lockdown can be prolonged

“The whole city is much emptier than usual,” he said.

“My morning commute took me half as long as it normally does, and a number of shops and banks around my office remained closed.” Mr Demicoli nevertheless said most people weren’tletting the tense atmosphere get to them.

“It’s not quite business as usual but it’s close to it,” he said. “People are aware of the situation because it’s right there in their face, but when you’re actually in it, you’re too busy doing your own thing to worry too much.”

Other Maltese people, however, painted a bleaker picture. Roberta Abela, who has lived in Brussels for three years, said she had never seen the city in such a state.

“Everywhere was completely dead yesterday and it still is today,” she said. “There was certainly tension in the streets because of constant controls by police and soldiers.”

Ms Abela said many people had visited friends’ homes rather than go out in the evening, partly because so many places were closed but also out of fear.

The Maltese foreign ministry has not yet issued any official advice for travel to Brussels, while those contacting the ministry have simply been told to exercise caution and observe instructions from the Belgian authorities.

Belgian Prime Minister Charles Michel last night announced the metro system and schools would re-open only on Wednesday.

Meanwhile, amid the tension, a lighter response to the crisis sounded on Sunday night.

Responding to a request from authorities not to disclose details about police activity on social media, Belgian Twitter users flooded the hashtag #BrusselsLockdown with pictures of cats.

This was to make it harder for suspects to uncover information about the anti-terror measures.