A suspect has been arrested over the killing of four people at Brussels’ Jewish Museum last Saturday.

Mehdi Nemmouche, a French citizen from the northern French town of Roubaix, was taken into custody in Marseille on Friday. He was said to have in his possession a gun and a Kalashnikov assault rifle of the sort used in the May 24 attack.

Nemmouche is believed to have links to Syrian jihadists.

"We will monitor those jihadists and make sure that when they come back from a fight that is not theirs, and that is definitely not ours ... they cannot do any harm," French President Francois Hollande was cited by Reuters as saying.