The same gun used to kill three children and a rabbi at a Jewish school in France had been used to kill three French soldiers, sources have claimed.
Jerusalem rabbi and religious studies teacher Yonathan Sandler and his two sons aged three and six, Aryeh and Gavriel, were killed in the attack at the Ozar Hatorah school in Toulouse, and a 10-year-old girl, Miriam Montenago, daughter of the school's principal Rabbi Yaakov Monsonego, was also killed.
A 17-year-old boy is critically injured. Mr Sandler had moved to France from Jerusalem in September.
The attack bore strong similarities to two shootings in the same region earlier this month, where a gunman riding a scooter killed three French soldiers. All were said to be of ethnic minorities.
A French police official said the same large calibre pistol was used in all three attacks.
A minute's silence will be held in all French schools at 11am Tuesday in memory of the victims
French election candidates have expressed their sorrow and President Nicolas Sarkozy and Socialist candidate Francois Hollande. Mr Sarkozy called it an "abominable and terrible tragedy".
Education Minister Luc Chatel and Richard Prasquier, president of the Representative Council of Jewish Institutions in France (CRIF) will accompany the President.
Mr Hollande expressed his "solidarity with the families and the Jewish community of France", adding "the whole nation is in mourning."
Israeli Prime Minister Benjamin Netanyahu said: "Today we had a savage crime in France that gunned down French Jews, among them children. It’s too early to say what the precise background for this act of murder is, but I think that we can’t rule out that there was a strong murderous antisemitic motive here.
"I’m sure that Nicolas Sarkozy, the President of France, and his government will do their utmost to find the killer and we, in Israel, will do everything to help them in this task."