Belgium has charged two new suspects over last month’s deadly Brussels airport and metro attack

Belgium has charged two new suspects over last month's deadly Brussels airport and metro attacks, as police pursue the investigation "night and day", the federal prosecutor's office said on Tuesday.

A statement said Smail F. and Ibrahim F. were "charged with participation in the activities of a terrorist group, terrorist murders and attempts to commit terrorist murders, as a perpetrator, co-perpetrator or accomplice."

The prosecutor said there were "indications" the two men could be linked to the rental of an address in the Etterbeek district of Brussels which was raided last week.

At the time, police said they found nothing of interest there but reports suggested that two men -- including Khalid El Bakraoui, who later blew himself up in the Maalbeek metro station -- may have stayed or used the address.

The second man, later identified as Swedish national Osama Krayem, was seen on CCTV with Khalid at a nearby metro station on March 22, apparently also carrying a rucksack bomb.

Khalid then got on the metro, travelling to Maalbeek station near the European Union headquarters district in Brussels.

Krayem was arrested last week and charged with terror offences.

The federal prosecutor gave no further details in Tuesday's statement about Smail F. and Ibrahim F., citing the need for secrecy "in the current state of the investigation which is continuing actively, day and night."

The airport and metro bombings killed 32 people in Belgium's worst terror attack which was claimed, like the attacks in Paris in November, by the Takfiri group, ISIL (so-called Islamic State in Iraq and Levant).