TOULOUSE, France — France's president is vowing to fight terrorism and anti-Semitism on online social networks and beyond, as he pays homage to four people killed at a Jewish school in the country's worst terrorist attack in years.

Francois Hollande said anti-Semitism "will be chased out everywhere . . . in particular on social networks where anonymity is granted to hatred."

He pledged "no weakness" against terrorism. He was speaking Thursday at the school in Toulouse where a radical Islamist Frenchman killed three children and a rabbi in the March attack.

Hollande pledged to find out why the gunman was not stopped earlier despite having been under surveillance by French authorities.

Hollande pledged to protect Jewish children and all those targeted for their religion.

Israeli Prime Minister Benjamin Netanyahu also took part in the ceremony.