At least 40 people were arrested in the French capital Saturday after an anti-Israel protest involving several thousand people turned violent, media reports said.

Waving Palestinian flags and chanting slogans to show their support for Palestinian people, demonstrators took to the capital’s streets at 3 p.m., Xinhua reported citing BFMTV news channel. Some 2,000 policemen were deployed to ensure peace during the protest.

The anti-Israeli rally turned violent after masked men in the Parisian square, La Place de La Republique, launched projectiles at the riot police, who reportedly responded by firing tear gas.

An Israeli flag was also burnt to denounce Israel’s attack on Hamas-controlled Gaza that has left at least 1,000 dead, mostly civilians.

“Violence, mainly anti-Semitic violence exists. We must face it…The organisers of the rally scheduled…are responsible for any uncontrolled behaviour and become subject to criminal penalties,” Interior Minister Bernard Cazeneuve said.

In a recent interview, French President Francois Hollande said: “I say very strongly: there will be no tolerance for any particular intrusion or uncontrolled behaviour because anti-Semitism cannot be used because of the conflict between Israel and Palestine.”