The arrest of Paris attacks suspect Mohamed Abrini in raids linked to the Brussels airport and metro bombings on Saturday highlighted the ties between jihadists involved in Belgium and France's worst terror outrages.
The March 22 Islamic State attacks in Brussels represented a security "failure", Belgian Prime Minister Charles Michel admitted, but he rejected the notion his country was a "failed state".
Brussels Airport is to reopen Sunday, 12 days after its departure hall was wrecked by Islamic State suicide bombings, with chief executive Arnaud Feist announcing three flights.
Brussels main airport failed to reopen on Friday evening as planned because police and airport authorities could not agree on how to screen passengers arriving for flights following the March 22 suicide bombings.
Indian Prime Minister Narendra Modi said his country shared Belgium's pain over the Brussels attacks as he added a wreath of white flowers to a sea of tributes outside Maalbeek metro station.
The sole suspect charged over last week's Brussels attacks was released on Monday following a lack of evidence linking him to the carnage, Belgian prosecutors said.
Belgian police on Monday released new video footage of the third suspect whose bomb failed to go off at Brussels airport in last week's attack.
An Algerian held in Italy as part of a probe into fake ID documents used by the Paris and Brussels attackers was interrogated on Sunday but refused to answer questions, a judicial source said.