Two of the suspects, who were arrested in the Spanish city of Melilla on the northern coast of Africa, spread IS material on various Internet platforms, translating it into Spanish in order to reach more people, the ministry said.
The two men were working to recruit women who, after a process of indoctrination, ended up joining the militant group.
In addition to online activity, the suspects organized meetings in private homes, where they showed propaganda material to potential IS members. Some of the young people recruited by the suspects had already begun preparations to travel to conflict zones, the ministry said.
The arrests follow a recent string of anti-terrorism raids across Europe. Last month, another four suspected jihadists were arrested in Spain.
Thousands of European nationals have, according to Europol, traveled to the Middle East to join jihadist groups such as the notoriously brutal Islamic State, which has made major advances in Syria and Iraq over the past year.