"This is a big problem that affects not only Iraq, but is going to spread to other parts of the world. Many jihadis come from Europe, and on their return they will be sleeper cells," he said in an interview with French radio station Europe 1.
Masum, who is in Paris to attend the international conference on peace and security in Iraq, stressed the need to "act quickly" because otherwise the IS would make more territorial gains in neighbouring Syria as well.
The Iraqi president reiterated that his country did not need troops on the ground from the international coalition, but rather military air support and finding ways to cut the funding of the terrorist group.
"Arab countries have an important role to play. We need their support," said Masum, who will meet with French President François Hollande later Monday.
The conference, co-chaired by Hollande and Masum, brings together representatives from 24 countries, including the US, Germany, Saudi Arabia and Egypt, as well as the Arab League, the UN and the European Union.