Belgium has reduced the threat level for Brussels from the highest level.
The capital, which has been on virtual lockdown for nearly a week, is now at level three, which means there is a ‘possible and real threat’.
Over-ground trains, including international services, airports, trams and buses are operating as usual.
The Brussels metro network is expected to resume normal service from Friday with additional security in place.
The UK Foreign and Commonwealth Office advised visitors to remain alert and vigilant.
"There have been a number of police raids in the Brussels Region and other Belgian cities in the past week. Belgian security operations are likely to be carried out at short notice," it said.
"If you’re in an affected area you should follow the instructions of the Belgian security authorities. Police have asked the public not to comment on police operations on social media."
Belgium raised the threat to level 4 for Brussels following the terror attacks in Paris on November 13.
Patrick Bontinck, CEO of Visit Brussels, said: "These were difficult days for Brussels, but we never lost confidence in our security services.
"The decision to raise the threat level to the maximum in Brussels was made for our own safety, that of residents and visitors. The fact that public policies didn’t hesitate to raise the alert level to 4 shows that no risk was taken regarding the safety of residents and visitors. It is therefore no exaggeration to say that in Brussels, the safety of all comes before the economic interests.
"Of course, this ‘Brussels Lockdown’ was not easy. Like all other locals, we as a tourism office had to face an unprecedented situation. We were in constant contact with the regional government, the tourist services of the two other Belgian regions and our tourism partners in Brussels.
"Thanks to this collaboration we managed to communicate on the situation as much as possible in an open way to tourists whom were present in Brussels as potential visitors. Especially the Brussels hotels were an important partner in the care of visitors present in our capital the weekend of November 21."
Increased security measures have been put into place at the Davis Cup Final, due to be held in Ghent this weekend, including additional checks at all entrances to the venue.
"These will apply to all ticket holders, staff members and visitors, so allow time in your travel plans for any delay this may cause," says the FCO advice.
It added: "Some public events may be cancelled and some tourist attractions closed. Contact event organisers for information on whether specific events are going ahead."
Meanwhile, border controls have been reintroduced at all ferry crossings from Sweden, Denmark and Germany.
There will also be additional border controls on the Sweden/Norway land border, so travellers must carry a valid passport on all these routes.
