One suspect died and four police officers wounded in the raid. Belgian police fear that two people are on the run following the operation in Brussels earlier Tuesday, a senior Belgian counterterrorism official told CNN.
A CNN crew arriving at a train station in the Belgian capital noticed a large police presence and heard helicopters over the area where the raid took place.
On Tuesday evening, Belgium Prime Minister Charles Michel told reporters that police operations were ongoing in the neighborhood.
Police went to search a presumably empty apartment Tuesday afternoon in southern Brussels, only to have people inside begin shooting at them, the counterterrorism official said.
A witness in Forest -- the southern Brussels district where the raid occurred -- heard about 30 shots early in the confrontation, including some from a suspect firing what appeared to be a rifle at police.
"I ended up in the middle of terror here in Brussels," the man said.
Three police officers -- including a French police woman -- were wounded in an initial burst of gunfire, with a fourth hurt later. Two of them were treated and released from a hospital, Deputy Prime Minister Jan Jambon said.
South Brussels police spokeswoman Marie Verdete initially indicated that three officers suffered slight injuries in two shootouts in the same building, which is along Rue du Dries, a small and typically calm road.
Police searching for explosives and weapons found the body of a suspect who had been barricaded inside, said Eric Van der Sypt, a spokesman for Belgium's federal prosecutor. A Belgian federal prosecutor said the suspect, who had a Kalashnikov rifle, was killed by a Belgian police sniper.
It will take some time to identify the body, Van der Sypt said, but a preliminary examination indicates it is "most probably not" suspected Paris attacker Salah Abdeslam
Belgium a focus after Paris attacks
It's unknown what connection Tuesday's raid has to the November 13 carnage
in Paris. Belgium has been a focal point for investigators.
ISIS claimed responsibility
for the suicide bombings and gunfire that left at least 130 people dead and hundreds wounded.
European investigators focused intently on Belgium, especially Brussels, on the heels of the attack.
Earlier this year, a senior Belgian counterterrorism official told CNN that two terrorist operatives phoned in orders from Brussels
to those directly involved in the Paris attacks.
These two had an even more integral role than Abdelhamid Abaaoud -- the man long identified as the ringleader of the attacks -- according to the official.
Attack suspect not target of latest raid, sources say
Yet others with Belgian connections and ties to the November 13 attacks remain at large.
They include Abdeslam, a Belgian-born French national who lived and spent time with Abaaoud in a Belgian prison. The trail for Abdeslam, one of the few alleged Paris attackers to escape alive, went cold in December, according to a senior European counterterrorism official.
French sources close to the investigation said Abdeslam was not the target of Tuesday's raid. (French police were part of that operation, according to those sources.)
There are many reason authorities investigating the Paris attacks are in Belgium. Many of those tied to the Paris attacks live in the country, and they're believed to have met there before lashing out.
There is concern more individuals from the same place may be ready to launch other attacks.
Last month, investigators conducting a search in connection to what happened in Paris found about 10 hours of video surveillance of a senior Belgian nuclear official
, Belgian prosecutor's office spokesman Thierry Werts said. It's unclear if that footage was from before or after the November attacks.