Authorities killed one suspect in Tuesday's raid -- Belkhaid Mohammed, 35, an Algerian who had not been on authorities' radar before, spokesman Eric Van der Sypt said in a statement.
He said a special forces sniper killed Mohammed when he tried to open fire on police from a window.
The Algerian's body was found next to a rifle and a book on Salafism, a puritanical branch of Islam that dictates only the followers of the Prophet Mohammed practice the correct Islam. Authorities also discovered 11 loaded Kalashnikov magazines "and innumerable shell casings," but no explosives, according to Van der Sypt.
An intense manhunt followed Tuesday's operation in the southern Brussels neighborhood of Forest, which authorities connected to the investigation of the Paris terror attacks
that killed 130 people in November.
One man was taken in for questioning during a subsequent house search Tuesday night in Brussels. And police also arrested an injured man who'd been taken to a hospital in Halle, a city about 12 miles (20 kilometers) south of Brussels.
But the Belgian federal prosecutor's office said Wednesday that both men were later let go without being charged.
The raid began around 2:15 p.m. (9:15 a.m. ET) Tuesday when four Belgian and two French police officers arrived at what was thought to be an empty residence in Forest, according to a senior Belgian counterterrorism official.
Instead, Van der Sypt said, "From the moment that the door of the flat was opened, at least two persons ... opened fire toward them."
Three officers -- including a Frenchwoman -- were hurt in the initial exchange of gunfire before managing "to retreat safely," he said.
Reinforcements arrived, with bullets flying back and forth for several hours. Another officer, from Belgium, suffered a slight injury to the head in the later exchange.
Two of the four wounded officers already had been treated and released from an area hospital as of early Wednesday, according to Belgian Deputy Prime Minister Jan Jambon.
Afterward, authorities found another Kalashnikov in a building near the site of Tuesday's raid. But other searches came up empty.
Belgian troops will help police in their anti-terrorism efforts, Prime Minister Charles Michel said.
There's no change in Belgium's threat level, now at its second highest, though the Prime Minister acknowledged Tuesday's bloody raid underscored the need to be on guard.
"The terrorist threat level is maintained at level three as yesterday's events confirm the threat is still real," Michel said.
Four people suspected of planning a terror attack were arrested Wednesday morning in Paris, French Interior Minister Bernard Cazeneuve said.
The four suspects, three men and a woman, were taken into custody.
A source close to the investigation told CNN that police moved in to make arrests in Paris after individuals discussed launching an attack in the city. So far the plot appears to be only aspirational in nature. Police have not recovered evidence pointing to concrete planning, the source told CNN.
Cazeneuve, speaking to French media, said intelligence services are making arrests and carrying out terror-related investigations every day and called for "prudence." He confirmed that authorities found a starter pistol with one round but no other arms or weapons.
Belgium a focus
It's unclear what connection Tuesday's raid has to the November 13 carnage
Belgium long has been a focal point for investigators.
Two terrorist operatives phoned in orders from Brussels
to those directly involved in the Paris attacks, according to a senior Belgian counterterrorism official.
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.
In his remarks Wednesday, Van der Sypt noted that authorities have searched more than 100 houses and arrested 58 people as part of the post-Paris probe. Another 23 people have been arrested "in linked investigations."
Fear of more attacks
Yet others with Belgian connections and ties to the November attacks remain at large.
They include Salah 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.
Many of those tied to the Paris massacre lived in Belgium, and they're believed to have met there before planning attacks.
There is concern more individuals from the same place may be ready to launch other attacks.