The United Nations and Israel led world condemnation of the shooting of three children and a teacher at a Jewish school in France on Monday, with Prime Minister Benjamin Netanyahu calling it “despicable murder,” as New York police beefed up security around synagogues and Jewish institutions.

Children aged four, five and seven, and a 30-year-old religious education teacher, the father of two of the young victims, were shot dead on Monday as they arrived for classes at the Ozar Hatorah school in the southwestern city of Toulouse.

The killer, riding a powerful scooter, is suspected to be the same gunman who shot dead three soldiers of Arab origin in two incidents earlier this month in Toulouse and nearby Montauban.

“In France today there was a despicable murder of Jews, including small children,” Netanyahu told a meeting of his Likud party.

“It is too early to determine exactly what the background to the murderous act was, but we certainly cannot rule out the option that it was motivated by violent and murderous anti-Semitism.”

On the other side of the Middle East conflict, Palestinian negotiator Saeb Erakat also expressed his outrage, saying: “We strongly condemn all terrorist operations, and in particular the attack today in Toulouse.”

U.N. Secretary General Ban Ki-moon condemned the killings “in the strongest possible terms.”

Ban was “saddened by the tragic deaths” of the three children and the father of two of the dead children in the shooting in the southwest city of Toulouse, said U.N. spokesman Martin Nesirky.

France has launched a massive manhunt for the serial killer, slapping an unprecedented terror alert on the southwest of the country.

With a grieving nation in shock, President Nicolas Sarkozy has declared a minute’s silence to be observed in all schools on Tuesday at 11:00 am (1000 GMT).

Monday’s massacre was the third fatal shooting in the Toulouse area in eight days by a killer using the same weapon and a stolen scooter. His first target was a paratrooper of North African origin, shot dead in Toulouse on March 11.

Four days later the cold-blooded killer shot dead two other soldiers of North African origin in the nearby garrison town of Montauban, also seriously wounding a soldier from the Caribbean.

French President Nicolas Sarkozy suspended his re-election campaign until at least Wednesday, as police probed the third fatal shooting in the Toulouse area in eight days.

“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.

In Washington, the White House condemned the “outrageous” and “unprovoked” shooting. “We were deeply saddened to learn of the horrific attack this morning,” said National Security Council spokesman Tommy Vietor.

Police Commissioner Ray Kelly said tightened surveillance and increased patrols at more than 40 locations citywide came in response to the Toulouse attack and not in response to a specific threat against New York City.

“We know that we’re the top of the terrorist target list, so we’re concerned about the so-called copy-cat syndrome where someone might see the events unfolding in Toulouse and take it upon themselves to act out,” Kelly told reporters, according to Reuters.

He said the additional coverage includes some undercover officers “but it’s largely increased uniformed presence at houses of worship and other locations.”

New York City, home to more than 1.4 million Jews, has the largest Jewish population of any metropolitan area outside of Israel, said Levi Fishman, spokesman UJA-Federation of New York.

The dead teacher was named by a relative as Jonathan Sandler, originally from Jerusalem, who had moved to France last year. He had dual Franco-Israeli nationality.

European Commission president Jose Manuel Barroso said: “I strongly condemn this odious crime and express the horror that this blind violence inspires. Nothing is more intolerable than the murder of innocent children.”

The Vatican also voiced outrage, with spokesman Federico Lombardi condemning the “horrific and heinous act,” noting that it followed other “senseless violence” in France.

Australian Prime Minister Julia Gillard called the killings “an act of irredeemable evil.”

British Foreign Secretary William Hague spoke of an act of “calculated cruelty” which he said would “unite all decent people in revulsion and condemnation.”

Meanwhile Italian Prime Minister Mario Monti expressed “outrage and alarm,” stressing that “anti-Semitism, xenophobia and intolerance are utterly contrary to the… values that underlie all of humanity.”

His Spanish counterpart Mariano Rajoy said he was “shocked by the cruelty,” and his Belgian counterpart voiced his “horror and indignation.”

German Foreign Minister Guido Westerwelle was swift to stress that “anti-Semitism and violence against Jewish institutions or people of Jewish faith have no place in Europe and must be rigorously punished.”

Poland’s foreign ministry said: “Such acts of terror can have no justification and must be condemned unreservedly by the civilized world.”

Belgium, the Netherlands and Sweden also stepped up security around Jewish schools and other buildings, while European Jewish groups urged France to catch the gunman. There were expressions of outrage from Jewish groups on other continents.

“While many of the details are still emerging, it appears that this was a premeditated attack with the intention to murder Jewish children,” said Moshe Kantor, president of the European Jewish Congress.

Canadian Minister of Foreign Affairs John Baird sent a message on his Twitter account Monday morning expressing his “solemn and sincere condolences to those affected by the shootings at Toulouse,” as Canada’s Jewish community said it shared “the terrible pain” being felt in Toulouse and beyond.