French police conduct their investigation outside the Ozar Hatorah Jewish school in Toulouse, southwestern France
A man on a scooter opened fire outside the school, killing two children and one adult, a police source said

A gunman opened fire at a Jewish school in the south-west city of Toulouse in France, killing four people including three children.

At least four people were killed after a gunman opened fire outside the Ozar Hatorah School, a private Jewish secondary school in Toulouse.

The adult is thought to be a rabbi who taught at the school. Two of his children, aged three and six years old, were also killed in the attack.

The fourth victim, also a child aged between eight and ten years old, is believed to be the school's principal's daughter.

A 17-year-old teenage boy is also said to be seriously injured.

Witnesses said a man, armed with two weapons opened fire outside and then inside the school before fleeing on a black scooter.

"I saw two people dead in front of the school, an adult and a child ... Inside, it was a vision of horror, the bodies of two small children," a distraught father whose child attends the school told RTL radio.

"I did not find my son, apparently he fled when he saw what happened. How can they attack something as sacred as a school?"

AFP news agency said the gunman initially used a 9-mm weapon, but it jammed so he switched to a .45 calibre weapon.

The shooting has shocked France, and parents present at the school said the crime was motivated by anti-Semitism.

President Nicolas Sarkozy and Claude Gueant, the interior minister, had planned to visit Toulouse on Monday to drum up support for Sarkozy's re-election bid but said they would now cancel the events out of respect for the people affected by the attack.

Sarkozy, who visited the scene, described the killings as a "frightening tragedy".

Gueant and Francois Hollande, the Socialist party's candidate in next month's presidential elections, are expected to visit the school.

French authorities are still hunting the gunman.

Last week a man on a black scooter also killed three soldiers in two separate incidents. They were all of north African origin.

In all three attacks the gunman used a .45 calibre weapon, prompting speculations of a link.

President Nicolas Sarkozy said it is much too early to determine a definite link.

"Whatever happens," he explained, "faced with this kind of toll, we can say that the French Republic as a whole has been hit by this appalling tragedy."