However, the official MAP news agency reported only three as having been arrested.
The men were arrested on Saturday after an exchange of gunfire during an overnight police raid on a house in the Hay Hassani district on the southern outskirts of Casablanca.
One of those held was Abd al-Malik Bouizagarne, believed to be a top planner in the five coordinated attacks carried out by 12 human bombers on 16 May 2003.
MAP identified the others as Muhammad Jarmuni and Murad Lamnauar. Two of the three suffered bullet wounds in the legs.
Government sources said about half a dozen alleged Islamist fighters were cornered by security forces in Sid al-Khadir and that four, not three, people were arrested.
One was reported to be in a critical condition in hospital with bullet wounds. The two others escaped.
MAP said counterfeit money and sabres were seized, along with passports and identity cards belonging to other people.