Speaking at a summit of the Group of Seven (G7) leading industrialized nations in Brussels on Wednesday, Hollande said Paris is trying to prevent French nationals from going to Syria because the move can jeopardize France's security.

“We have decided on cooperation to prevent, deter and punish this type of movement, which can jeopardize our own security,” he said.

French Prime Minister Manuel Valls said on Tuesday that over 800 French nationals are fighting in Syria against the government or are planning to do so. The number was previously put at 300 to 400.

The French prime minister warned that the militants pose an unprecedented security threat when they return home.

“We have never before faced a challenge of this kind. It is without any doubt the most serious threat we face,” Valls said.

The warning followed the recent arrest of a French national suspected of murdering three people at a museum in Brussels after spending a year fighting in Syria.

Western officials are concerned that the militants, who have obtained military skills in Syria, would return to their countries and carry out terrorist attacks on home soil.

Syria has been gripped by deadly violence since March 2011. Over 160,000 people have reportedly been killed and millions displaced due to the violence fueled by the foreign-backed militants.

NTJ/NJF