Those confined overnight are associated with plotting a terrorist assault, prosecutors say. They were among 40 taken in for addressing.
Quests were directed in 16 districts, for the most part around Brussels, with keeps an eye on 152 lock-up carports.
PM Charles Michel said security would be ventured up at open occasions.
He tweeted (in French) after a meeting of the Belgian security committee to say occasions would proceed as arranged and he asked the general population to resist the urge to panic.
As indicated by a report by open telecaster RTBF (in French), terrorism suspects were seen driving on Friday almost a fan zone in focal Brussels, where Saturday's Euro 2016 match amongst Belgium and the Republic of Ireland is because of be handed-off from France by goliath screen.
On 22 March, bombs executed 32 individuals at a Brussels air terminal and a metro station.
No arms or explosives were found amid the pursuits, which went off without episode, Belgium's government prosecutor said in an announcement.
Among the territories where looks occurred was Molenbeek, a Brussels area which has ended up infamous in light of its relationship with jihadists.
The government prosecutor said the operation had been dispatched after examinations which "required a prompt mediation".
The nation is under a level 3 dread ready, one underneath most extreme.
"It is not over," Interior Minister Jan Jambon was cited as saying by Associated Press news organization on Saturday.
"We stay under dread ready three. It implies that something is still up. The previous evening, we had an exceptionally fruitful activity."
On Friday evening, four government clergymen including Mr Michel were set under increased police assurance alongside their families, Belgian media report.
An anonymous security source was cited by Belgian daily paper DH (in French) on Wednesday as saying the gathering had "left Syria around a week-and-a-half back meaning to achieve Europe by means of Turkey and Greece by vessel without international IDs".
In the interim, a Belgian national named as Youssef EA was captured on Friday and charged on suspicion of terrorist exercises regarding the March assaults, which were asserted by IS.
Belgian media report that he is the eighth individual to have been charged over the assaults, which were done by three suicide aircraft.
Agents have set up associations between the Brussels aircraft and the IS assaults on Paris on 13 November, in which 130 individuals were murdered.
A few of the Paris planes originated from Belgium and a portion of the bombs were made in a level in Brussels.
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