"Numerous elements in the investigation have shown that the terrorist group initially had the intention to strike in France again," the Belgian prosecutor's office said in a statement.
Investigators say that the same ISIS network was behind the Paris terror attacks in November and the suicide bombings in the Belgian capital last month.
When the terrorists discovered French investigators were moving fast
in their investigation of the November attacks, they changed their plans, the Belgian prosecutor's office said.
"Eventually ... they urgently took the decision to strike in Brussels," the prosecutor said.
Salah Abdeslam, a key suspect in the Paris attacks, was arrested by police in Brussels on March 18. Just four days later, suicide bombers struck at the city's airport and subway station, killing 32 people.
The terror cell had planned to attack high-profile targets in Paris, CNN affiliate BFM reported, citing a source close to the investigation.
A laptop recovered by investigators in Brussels last month included a list of targets in Paris including the financial district, known as La Defense, and a Catholic association, BFM reported.
In November, Paris prosecutor Francois Molins said that investigators had learned that Abdelhamid Abaaoud, the ringleader behind the Paris attacks in November, had planned a suicide attack on La Defense.
Days after the attacks in Paris, Abaaoud was killed in a police raid. So was his female cousin Hasna ait Boulahcen.
Police had received a tip from a female confidential witness.
The witness told police she'd hosted Boulahcen in her home since October, according to documents, and that two days after the Paris attacks, Boulahcen received a phone call when the two of them were together.
The person on the other end of the line asked Boulahcen to find a vehicle and pick someone up in an industrial zone on the outskirts of Paris. The witness goes with Boulahcen and a man steps out from behind a bush. The witness later learns that the man was Abaaoud, the documents say.
The witness told police he wore orange sneakers and claimed he had taken advantage of refugees to come to France to carry out attacks.
'Man in the hat'
announcement came a day after authorities identified Mohamed Abrini,
believed to be the third and lone surviving suspect in the Brussels airport attacks.
Authorities said Abrini confessed to being the "man in the hat." He was seen in Brussels airport surveillance images wearing a dark hat and rolling luggage carts with two men believed to be the suicide bombers.
Authorities charged him with participation in terrorist activities, terrorist murders and attempts to commit terrorist murders, the prosecutor's office said.
Abrini is one of six people detained in raids
Friday across the Belgian capital. In addition to the Brussels attack, he has been tied through surveillance video and DNA to November's terror attacks in Paris. Those attacks killed 130 people.
Earlier Saturday, the prosecutor's office said it identified the second person seen in surveillance footage from the subway attack in Brussels.
Osama Krayem -- also known as Naim al Hamed -- is seen along suicide bomber Khalid El Bakraoui, according to the Belgian federal prosecutor's office.
He has also been charged with "participation to the activities of a terrorist group and terrorist murders," according to the prosecutor's office.
European security agencies believe Krayem, or Hamed, played an operational role in the attack.
Belgium has emerged as a hotbed of extremism, exporting more foreign fighters per capita to Syria than any other Western European nation, according to the International Center for the Study of Radicalization and Political Violence.
The Brussels and Paris attacks "point to a broad and sophisticated terrorist network in Belgium," the London-based think tank said.