Hollande made the comments before a meeting in Paris with former Israeli President Shimon Peres and after three suspects were arrested in raids related to the investigation surrounding the Paris and Brussels attacks, which have been claimed by ISIS.
Another man, with no apparent links to the Paris or Brussels attacks, was arrested during raids in Paris Thursday that officials said prevented a terrorist attack.
"We have had success in finding the terrorists and both in Brussels, and in Paris there have been some arrests and we know there are other networks, because even though the one that carried out the attacks in Paris and Brussels is in the process of being wiped out — with a number of its members arrested — there is still a threat looming," Hollande said.
An initial review has uncovered no forensic evidence to indicate the Brussels airport bombers specifically targeted Americans in the attack, a senior U.S. law enforcement official said. The bombs appear to have been detonated where they would cause maximum casualties regardless of nationality, the official said.
U.S. House Intelligence Committee Chairman Devin Nunes on Thursday suggested the attack might have been intended to kill U.S. citizens, but cautioned it was his own assessment and he had no evidence to support his view.
Five suspects have been identified in connection with the three bombs detonated in two different travel hubs in Brussels. Of the three suspects who were killed by the bombs, one, Najim Laachraoui, is tied to making bombs used in the November Paris attacks, while two brothers, Khalid and Ibrahim El Bakraoui, who are suspected in the Brussels attack were also being sought in connection with the Paris massacre.
Two suspects are still wanted, authorities said. Naim al-Hamed — described as "armed and very dangerous" — is a Syrian on a list of suspects circulated to security services in other European countries, Belgian newspaper De Morgen and news site DH reported, citing police. He is also thought to have been involved in the Nov. 13 attacks in Paris. NBC News was unable to immediately confirm the reports.
Investigators are also searching for Mohamed Abrini, who was filmed on security footage at a gas station with Salah Abdeslam, one of the alleged Paris attackers, just two days before the massacres. Abdeslam was captured four days before the attacks in Brussels.
While the two suspected terrorists remained unaccounted for, Peres sought to lend comfort Friday. "We're in the same struggle against terror. And in my view there is no doubt that the majority of people is against terror and for peace and the terrorists are a minority," he said.
Also Friday, the Belgium Foreign Office on Friday disclosed the nationalities of nine of the 31 killed in the attacks — two Americans, three Dutch citizens, and one citizen each of France, the United Kingdom, China and Peru.
Two of the Dutch victims lived in New York, NBC News learned. The siblings, Sascha and Alexander Pinczowski, who were Dutch nationals, had been due to fly back to the U.S. at the time of the blasts. They intended to become U.S. citizens, according to Jim Cain, the former U.S. ambassador to Denmark, whose daughter, Cameron, was dating Alexander.
The Pinczowskis hadn't been heard from since their phone line went dead while they were on the phone with a relative during the bombings.
This story first appeared on NBCNews.com.