The gunman is also a prime suspect in the killing of three soldiers in two separate shootings last week in Toulouse an d the nearby town of Montauban, to the north.
French police scoured southwestern France on Tuesday to find a gunman who shot dead three children and a rabbi at a Jewish school in the city of Toulouse, prompting President Nicolas Sarkozy to put the region on its highest terrorism alert.
More than 100 police officers were dispatched to the area to hunt for the gunman, who is also a prime suspect in the killing of three soldiers in two separate shootings last week in Toulouse an d the nearby town of Montauban, to the north.
Security was tightened in Toulouse, guards were posted at religious sites and the terror alert level raised to scarlet, meaning 'imminent attack', for the Midi-Pyrenees region.
Sarkozy said the killings at the school and those of the soldiers, one of Caribbean and two of Muslim origin, appeared to be motivated by racism. "In attacking Jewish teachers and children, there seems to be an obvious anti-Semitic motivation," he said late on Monday. "With the soldiers ... one can imagine that the bloodthirsty madness was linked to racism."
Police had not named a suspect but said they were searching the city of around one million for a man they believed could be a trained marksman, as well as the Yamaha motorbike he used to flee. The shooter's face was hidden by a motorcycle helmet during the attack.
A female witness told French television the gunman appeared to have a tattoo on his face when he lifted his visor.
One weapon, a powerful automatic handgun, had been used both in the school attack and last week's shootings of the soldiers. In the school attack the victims were a 30-year-old rabbi, his two children aged four and five, and a girl aged seven.
Video surveillance footage at the school showed the gunman shooting one child at close range in the head, before fleeing on a motorcycle, said Nicolas Yardeni, regional head of the French Jewish umbrella association, CRIF.
Police said the man's motorcycle, which they had identified by its licence plate, had been purchased last May. They were also looking into the possibility that the gunman could be one of three soldiers dismissed from the army in 2008 for neo-Nazi activities, magazine Le Point reported.
It was the most deadly anti-Semitic attack on French soil in nearly 30 years. In August, 1982, six people were killed in a combined grenade and gun attack at the Goldenberg restaurant in Paris' Marais Jewish district.
As night fell, students of the Ozar Hatorah Hebrew school gathered with the bodies of the victims for an all-night vigil.
Windows were shuttered at the school, a five-floor brick building in a leafy residential neighbourhood. The wall near the front gate bore bullet marks, and one window was shattered. Israel's embassy condemned the attacks as "appalling murders" and said it would arrange to transfer the coffins of the victims to Israel, where the rabbi had received his religious training.
In Paris, Sarkozy, Prime Minister Francois Fillon, several cabinet members, and Socialist presidential candidate Francois Hollande attended a memorial service at a synagogue, while thousands of Parisians held a silent march in honour of the victims.
Sarkozy, who is seeking re-election in a national poll held in two rounds in April and May, said he would suspend his campaign until Wednesday. Far-right chief Marine Le Pen, currently ranked third behind frontrunner Hollande and Sarkozy, also said she would suspend her campaign.
Sarkozyz called for a minute of silence at schools across the country at 1100 a.m. on Tuesday and said everything had to be done to track down the perpetrator.
Dominique Reynie, head of the Fondapol politics institute, said the election campaign, where the skirmishes had veered into aggression in recent days, could be transformed by the impact of the killings on public opinion, five weeks from voting.
"The tone of the campaign cannot go back to what it was," he told Reuters. "The campaign was dominated by an aggressive tone and a strong degree of populist rhetoric. This rhetoric will cease because there will be voter demand for healing."
Reynie drew a link between the rise of populist rhetoric and events such as the killing of 77 people last July by anti-Islam militant Norwegian Anders Behring Breivik, and with killings of foreigners in Italy and Germany in recent months.