The planners behind last month's bombings in Brussels which killed 32 people had initially planned to hit France for a second time but struck closer to home as investigators made arrests among key suspects, Belgian prosecutors said.
Investigations into the 13 November Paris attacks which killed 130 people showed many of the attackers lived in Belgium, including key suspects Salah Abdeslam and Mohamed Abrini who evaded police for four months after November's killings.
Abrini was arrested on Friday and admitted to having participated in the Brussels airport bombings.
He has been charged with terrorist murders, prosecutors said.
"Numerous elements in the investigation have shown that the terrorist group initially had the intention to strike in France again," Belgium's federal prosecutor said in a statement.
The attackers decided to hit nearby targets when Belgian investigators closed in on them.
Abdeslam, suspected of being involved in the Paris attacks, was arrested on the Friday before the Brussels bombings.
"Surprised by the speed of progress in the investigation, they took the decision to strike in Brussels," the prosecutor's statement said.
Belgium maintained its second highest threat level, with Prime Minister Charles Michel saying his government would remain alert.
Another main suspect who was seen alongside the suicide bomber in the Brussels metro and identified by prosecutors as Osama K was also arrested on Friday in the Belgian capital.
Osama K, 28, widely named by media as Swedish national Osama Krayem, was filmed buying the bags used to carry the Brussels bombs.
Like Abrini, his fingerprints were found in an apartment used as a bomb factory and safe house for the attackers.
As with other suspects in both the Paris and Brussels attacks, police believe Krayem returned last summer from fighting with the so-called Islamic State in Syria aboard refugee boats reaching Greek islands.
