Paris terror attack suspect Mohamed Abrini has been charged with taking part in a terrorist organisation, Belgian federal prosecutors said.

Abrini was arrested in Belgium on Friday but prosecutors said it is still unclear whether the 31-year-old is the "man in the hat" Brussels airport bombing suspect.

Prosecutors said they also charged Osama K, saying he was present at the time of the attack on the Brussels metro station on March 22, and a Rwandan national named as Herve B.M with taking part in a terrorist organisation.

Two people arrested with Abrini have been released, prosecutors added.