PARIS (Reuters) - Two suspected associates of the killer of a French police commander and his partner will be placed under investigation on Saturday for membership of a terrorist organization, the Paris prosecutor's office said.

The police couple were stabbed to death outside their home in Paris in an attack claimed by Islamic State on Monday.

The magistrate's office said it had opened a judicial investigation into the deaths, focused on charges of assassination, sequestration and participation in a terrorist project.

"Charaf-Din Aberouz and Saad Rajraji (...) will be brought before a magistrate as part of the judicial investigation in order to be placed under investigation for membership of a terrorist group," the prosecutor's office said.

(Reporting by Matthias Blamont; Editing by Andrew Heavens)