Armed police guard Jewish and Muslim schools across the south of the country amid fears cold-blooded killer will strike again

Hundreds of armed police have blanketed southern France searching for a gunman presumed to be a racist, anti-Semitic serial killer who shot dead a rabbi and three children at a Jewish school and who may strike again, officials warned.

France has been plunged into shock, fear and political soul-searching a month before the presidential election.

Officials said the calculating killer who attacked at the school, and who may have used a camera around his neck to film himself, was the same gunman who struck twice last week, killing three French soldiers of North African origin, two of whom were Muslim, and seriously injuring a black paratrooper of French Caribbean origin.

The French president, Nicolas Sarkozy, said a "monster" was on the loose. The biggest manhunt in modern French history intensified, with a swath of south-western France down to the Mediterranean saturated with police and army carrying out road and transport checks and police guarding Jewish and Muslim schools and sites across France.

The state prosecutor, François Molins, said the killer was extremely determined and the attacks were premeditated. The killer now knew he was being hunted and was "susceptible" to strike again, he said.

The man had used the same high-calibre Colt 45 handgun and had fled on what was thought to be the same Yamaha scooter, which may have been stolen in Toulouse on March 6. During each attack he kept his motorcycle helmet on and put his gun to his victims´ temples. Witness accounts suggested he may have been wearing a small video camera around his neck or tied to his chest to film the attack for personal viewing or posting online, but this had not been confirmed. Investigators have scoured the internet to check if any film was posted online.

The gunman first struck at 4pm on 11 March when he shot dead Imad Ibn- Ziaten, an off-duty staff sergeant in the 1st Parachute Logistics regiment, who was standing outside a gym in Toulouse.

Ibn-Ziaten had placed an advert online to sell his motorbike, specifying that he was a soldier and giving his first name. The killer shot twice before escaping by motorbike. Investigators are scouring computer evidence to identify who could have viewed that advert and whether any previous adverts triggered the contact.

The second attack was four days later in nearby Montauban. Three paratroopers in uniform were shot while withdrawing money from a cashpoint near their barracks. Abel Chennouf, 26, and Mohamed Legouard, 24, died on the spot. A third soldier from the French island of Guadeloupe is in hospital. Investigators are reviewing more than 7,000 hours of CCTV footage from Montauban.

The gunman struck at Ozar Hatorah Jewish secondary school at 8am on Monday, shooting rabbi Jonathan Sandler, 30, in the head. He then chased a seven-year-old girl, shooting her at close range and returned to kill the rabbi´s two sons, aged three and six, firing at them as they lay on the ground.

The killer, who is thought to have a good knowledge of firearms, left no DNA traces.

French media said police had ruled out a link to three paratroopers suspended from a local regiment in 2008 for neo-nazi behaviour. The state prosecutor said all lines of inquiry were open, nothing had been ruled out.

In the quiet, leafy residential streets surrounding the Jewish school in Toulouse, many parents had kept their children home from school. "I´m afraid this monster will strike again," said Murielle Gavil. Candles burned all night outside the school where prayer vigils were held for the dead, who will be buried in Israel. "We have been knocked sideways," said one former teacher at the school.

French presidential candidates have suspended their campaigning. But amid a mood of shock on the streets the once invective-filled, sometimes populist tone of the election could be transformed by the killings.

Sarkozy´s critics, some within his own centre-right party, had long questioned the staunchly rightwing, populist slant of the campaign, in which he had courted the extreme right by promising to halve immigration, saying there were too many foreigners in France and criticising the slaughter of halal meat.

The interior minister recently said "not all civilisations are of equal value" and some, namely France´s, are worth more than others.

The centrist François Bayrou said the shootings were a symbol of a divided French society that was sick, where "stigmatisation" of different sectors of society was growing as high profile people pointed the finger and stoked emotions just because there were "votes to be gained from it".

"The tone of the campaign cannot go back to what it was," said Dominique Reynié, head of the Fondapol politics institute. "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."

Criminologists speculated that the killer may be a narcissist delighting in the media coverage. "It would be surprising if he stops now," one police officer involved in the investigation said. (guardian.co.uk © Guardian News and Media Limited 2012 03/20/12)