The Brussels-based Islamic State jihadists behind the Paris attacks planned a fresh strike in France but targeted the Belgian capital instead as police closed in, the federal prosecutor said on Sunday.
The prosecutor also announced that the so-called "man in the hat" Mohamed Abrini had been charged with "terrorist murders" over the attacks in Brussels last month.
Suicide bombers claimed 32 lives when they blew themselves up at Brussels airport and at a metro station on March 22 but left a trail for police leading directly to the November Paris attacks which killed 130 people.
"Numerous elements in the investigation have shown that the terrorist group initially had the intention to strike in France again," the Belgian federal prosecutor's office said in a statement.
"Surprised by the speed of the progress in the ongoing investigation, they urgently took the decision to strike in Brussels."