Clashes erupted in Paris on Sunday as thousands of people protested against Israel and in support of residents in the Gaza Strip, where a six-day conflict has left 166 Palestinians dead.

Several thousand demonstrators walked calmly through the streets of Paris behind a large banner that read “Total Support for the Struggle of the Palestinian People”.

But clashes erupted at the end of the march on Bastille Square, with people throwing projectiles onto a cordon of police who responded with tear gas. The unrest was continuing early Sunday evening.

Media reports said that hundreds of Jews were trapped inside a synagogue in the area and police units were sent to rescue them.

A person in the synagogue told Israel’s Channel 2 news that protesters hurled stones and bricks at the building, “like it was an intifada.”

Riot police dispersed the group, with two members of the Jewish community and six officers slightly injured in the ensuing scuffle, the source said.

The people were able to exit the synagogue at about 9 p.m., according to a picture posted to Twitter by the French Jewish Defense League, a far-right group.

A second synagogue was also attacked.

Six protesters were arrested, police said.

Prime Minister Manuel Valls condemned the attempted synagogue stormings “in the strongest possible terms”.

“Such acts targeting places of worship are unacceptable,” he said in a statement.

“I am profoundly shocked and revolted. This aggression towards the Jewish community has taken an absolutely unacceptable turn,” Joel Mergei, president of the Israelite Central Consistory of France, told AFP.

Paris Mayor Anne Hidalgo called for “calm in the face of tensions” in the Middle East.

In the northern city of Lille, meanwhile, between 2,300 and 6,000 people protested peacefully, according to differing figures provided by the police and organizers.

The descent into violence in the Gaza Strip began on June 12 when three Israeli teenagers were kidnapped and later murdered, triggering a major military crackdown on Hamas in the West Bank and an escalation of rocket fire from Gaza.

Women hold a banner as they take part in a demonstration against Israel and in support of residents in the Gaza Strip,  on July 13, 2014, Paris. (photo credit: AFP/ KENZO TRIBOUILLARD)

Women hold a banner as they take part in a demonstration against Israel and in support of residents in the Gaza Strip, on July 13, 2014, Paris. (photo credit: AFP/ KENZO TRIBOUILLARD)

The revenge killing of a Palestinian teenager by Jewish extremists on July 2 added further fuel to the fire, turning into an all-out conflict on July 8 when Israel launched an air campaign against Gaza terrorists, trying to stem the rocket fire from the Hamas-controlled enclave.

The Palestinian death toll from Israel’s punishing air campaign has hit 166.

So far, no Israelis have been killed, although terrorists in Gaza have pounded the country with nearly 800 rockets since the fighting began and a further 150 have been intercepted by the Jewish state’s Iron Dome defense system. Two elderly people died of heart attacks over the weekend when sirens wailed.

Protesters hold placards calling for the boycott of Israel and one depicting French president Francois Hollande with the word "assassin", on July 13, 2014 in Paris, during a demonstration against Israel and in support of residents in the Gaza Strip, where a six-day conflict has left 166 Palestinians dead.  (photo credit: KENZO TRIBOUILLARD / AFP)

Protesters hold placards calling for the boycott of Israel and one depicting French president Francois Hollande with the word “assassin”, on July 13, 2014 in Paris, during a demonstration against Israel and in support of residents in the Gaza Strip, where a six-day conflict has left 166 Palestinians dead. (photo credit: KENZO TRIBOUILLARD / AFP)

“I came to say no to this massacre,” Amid Hamadouch, 30, told AFP at the Paris protest while it was still peaceful, with a sticker reading “Boycott Israel, Racist State” on his jacket.

“They are bombing innocent people. There are missiles being launched by Hamas, but the Israeli response is disproportionate. They are attacking the civilian population and not Hamas officials.”

The crowd, very young, shouted slogans such as : “We Are All Palestinians!” and “Only One Solution, End the Occupation!”.

Many protesters carried banners on which they had stuck photos taken from the Internet, reportedly showing Palestinian children killed or injured, houses razed to the ground or clouds of smoke emerging from bombed districts in Gaza.

According to the UN Office for the Coordination of Humanitarian Affairs, a majority of those killed in Gaza so far — 70 percent — have been civilians, of whom 30 percent were children.