France imposed an unprecedented terror alert in the southwest as police Tuesday sought a suspected serial killer who gunned down three children and a teacher at a Jewish school in Toulouse.

People light candles during a march in Paris on March 19, 2012 after the shooting at the "Ozar Hatorah" Jewish school in the southwestern city of Toulouse. , Photo: AFP

With the country in shock, President Nicolas Sarkozy suspended his election campaign until at least Wednesday, as police probed the third fatal shooting in the Toulouse area in eight days by a gunman using the same pistol and a stolen scooter.

Distraught and often angry parents converged on the scene shortly after the shooting as frightened children were brought out in small groups.

"I came to the school this morning for prayers," said six-year-old Alexia. "Five minutes later we heard shots, and we were very afraid. We were gathered in a room and prayed together while we waited for our parents."

The killer initially used a nine-millimetre weapon but it jammed prompting him to switch to a .45-calibre gun as he stormed the school, police said.

French authorities stepped up security at Jewish and Muslim schools following the bloody assault on the Ozar Hatorah school, and Sarkozy said the terror alert in the Midi-Pyrenees region had been raised to "scarlet", its highest level, following Monday's shootings.

"In attacking children and a Jewish teacher, the anti-Semitic motive of the attack appears to be obvious," Sarkozy said in a nationally televised address after he returned to Paris from the scene of the shooting.

Israel led global outrage against the "despicable murders" and identified the dead as Franco-Israeli citizens: 30-year-old Rabbi Jonathan Sandler and his sons Arieh, 5, and Gabriel, 4, as well as seven-year-old girl Miriam Monsonego.

Witnesses said Sandler died trying to shield his sons, and that the gunman had chased Miriam, the daughter of the school head, into the school before shooting her in the head.

Yaacov Monsonego was praying in the synagogue attached to the school when another young pupil brought him the body of his slain daughter, witnesses said.

A fifth victim, a 17-year-old boy, was wounded, but local community leaders said he was expected to survive.

The killer wore a full face helmet and appeared calm and collected, carefully parking his scooter before opening fire, witnesses said.

Last week, three French paratroopers -- all of North African descent -- were killed in two similar incidents in the same southwestern region in which the attacker rode a scooter and wielded the same .45 calibre handgun.

"What is sure is that he has now acted three times, and we are concerned by the attitude of impunity that he has demonstrated," Interior Minister Claude Gueant said, admitting that police have "no clear leads".

"This tragedy has left the entire national community distraught," Sarkozy declared at the scene, his voice cracking as he sent condolences to the Jewish community and the Rabbi's wife who lost her husband and two children.

He said a moment of silence would be observed Tuesday in all French schools, adding that security would be stepped up around religious establishments in the region and police reinforcements deployed to hunt down the gunman.

Electioneering was effectively suspended but both the right-wing incumbent and his Socialist rival Francois Hollande rushed to Toulouse to pay their respects.

"We cannot back down in the face of terror," Sarkozy said. "Barbarism, savagery, cruelty cannot win. Hate cannot win. The Republic is too strong for that, much too strong."

France's press said the tragedy had brought a measure of unity to France during a period of political division ahead of next month's presidential election.

"In the space of a few hours the unity of the nation supplants the partisan rants and the bad-natured arguments among the presidential hopefuls," the regional Midi Libre daily said.

The scarlet alert allows authorities widespread powers to disrupt daily life and implement sweeping security measures, including potentially closing rail terminals and airports or even halting water supplies.

Mixed police and military patrols can be ordered. It is the last step in a ladder of terror alerts before a formal state of emergency.

Led by a Jewish students' group, thousands of Parisians later held a silent march through the east of the capital, passing by historic Jewish districts.

The Ozar Hatorah association runs a small religious school for 200 people in a quiet suburb of Toulouse, a city with a 25,000-strong Jewish minority.

The first victim in the trio of shootings died on March 11, a 30-year-old non-commissioned officer in a parachute logistics regiment who was in civilian clothes when he was shot dead in Toulouse at point blank range.

On Thursday, three more paratroopers based in nearby Montauban were shot while standing at a cash machine outside their barracks.

Two victims -- sappers from 17th Parachute Engineering Regiment aged 26 and 24 -- died on the spot. The third man, a 28-year-old from the same regiment, was left in a critical condition with spinal injuries.

Source: AFP