Prime Minister Charles Michel summoned security and intelligence chiefs for an emergency sitting of Belgium’s national security council on Wednesday after an armed suspect was shot dead following a raid linked to the Paris attacks.
One Belgian private broadcaster, VTM, said two further suspects had been detained but there was no confirmation.
Brussels police killed the unidentified person who had an assault rifle after four officers were wounded on Tuesday during what investigators had expected to be a routine search on an apartment in the south of the Belgian capital.
Michel told RTL radio on Wednesday morning that police planned further operations in the coming hours and days.
“The threat remains,” Michel said, adding that Belgium would review its level of alertness and consider possible extra measures during the day.
Brussels, headquarters of the European Union as well as Western military alliance NATO, was entirely locked down for days shortly after the Nov. 13 Paris attacks for fear of a major incident there. Several of those involved in the Islamic State shootings and suicide bombings were based in the city.
Brussels has maintained a high state of security alert since then, with military patrols a regular sight.
Police searched nearby buildings through the night in the Brussels borough of Forest but did not confirm Belgian media reports that they were hunting two further suspects.
One or more people opened fire on police as they opened a door of an apartment. One of the wounded, none of whom was in a serious condition, was a French policewoman. Ministers said the presence of French officers was a coincidence and there had been no expectation that the house search would yield much evidence.
Local mayor Marc-Jean Ghyssels told public broadcaster RTBF that police searches in Forest were over: “The area is totally cleared, totally secured and operations have ended,” he said.
People living in the area, who suffered hours of lockdown after the initial operation turned into a firefight, said they were shocked at the turn of events in their quiet neighborhood.
Schoolboy Maxime, 11, was at home sick when he heard gunfire and helicopters and saw masked commandos on a rooftop. “They had a huge weapon,” he said, adding he had been “very, very scared”.
Federal prosecutors, who have been coordinating the investigation in Belgium into the Paris attacks, were due to hold a news conference at 10:30 a.m. (0930 GMT)
Investigators believe much of the planning and preparation for the Paris assault was conducted in Brussels by young French and Belgian nationals, some of whom fought in Syria.
Belgian security forces have been actively hunting suspects and associates of the militants involved in the Paris attacks.
One of the prime suspects, 26-year-old Brussels-based Frenchman Salah Abdeslam, is still on the run. He left Paris hours after his brother blew himself up outside a cafe. Belgian authorities are holding 10 people who have been arrested in the months since the attacks, mostly for helping Abdeslam.
Belgium, with a Muslim population of about 5 percent among its 11 million people, has the highest rate in Europe of citizens joining Islamist militants in Syria.