Assailants threw a barrage of Molotov cocktails Thursday into a building they mistook for a Jewish synagogue located next door, the region's top official said.

Three youths picked up some 200 yards from the site were detained for questioning, police said, without providing more details.

The fire-bombing followed a string of attacks on Jewish targets in recent days that has coincided with heightened tensions in the Middle East. Two synagogues in Marseille, on the Mediterranean coast like Montpellier, were among the targets.

In the Thursday attack, two offices of the building that houses the Herault region's environmental offices were badly burned, police said. There were no injuries since the assault took place in the early morning when the building was empty.

Jewish leaders joined Prefect Daniel Constantin and Montpellier Mayor Georges Freche at the site.

"It's probably an act by young delinquents," Constantin said. "Visibly, there was no preparation ... since they mistook the building."

Late Wednesday, a bus belonging to a Jewish school in the Paris suburb of Aubervilliers was set afire in an attack that also damaged two cars, local officials said.

Late Tuesday, two assailants hurled gasoline bombs at a synagogue in Marseille. Another Marseille synagogue was burned to the ground Sunday.

Despite the attacks, Finance Minister Laurent Fabius, who is Jewish, said Thursday that "France is not anti-Semitic."

"There are anti-Semitic acts. They must be condemned with particular vigor," he said on Europe-1 radio.