The "illusion" that terrorist attacks are only a threat to Jews, and not all French people, is over, says a political consultant based in Paris.

David Khalfa said every citizen "will have to confront the threat and the changes it implies".

He told the Times of Israel that, since January's attack on the Charlie Hebdo offices, French Jews had been on alert and were more prepared for attacks.

"Now everyone is a target: it happened in coffee shops, in restaurants, in a concert hall, and I think it has changed the whole perspective of fighting terror," he said.

France's Jewish security community service, the SPCJ, has posted on Facebook detailed instructions to community leaders about how to keep their congregations safe.

360m people received Facebook messages that their loved ones were safe

Most Jewish communal activities planned in France this week were also suspended. On Sunday, the Jewish Federation of France (FSJU) put off the launch of its National Appeal for Tzedakah, a money-raising radio appeal for Jewish charities.

The Maccabi Centre, which runs sports clubs in Paris, also scrapped events, and the Cultural and University Jewish Space of Europe (ECUJE) cancelled Hebrew courses and synagogue services.

Israeli technology was involved in reassuring Parisians that their relatives were safe.

In the 24 hours after the attacks, 4.1 million people used Facebook Safety Check, a technology developed by the company's Israeli research and development department.

A spokesman for Facebook Israel said: "A total of 360 million people received messages that their loved ones were safe."

Safety Check is a feature Facebook has activated several times in the past, usually for natural disasters.

The Paris attacks were the first time it was used to enable people to "check in" and let others know they were safe after such an attack.

It had previously faced criticism for not doing so in previous terror incidents in places such as Baghdad, Beirut, and Kabul.

Alex Schultz, Facebook's vice-president of Growth, said: "We chose to activate Safety Check in Paris because we observed a lot of activity on Facebook as the events were unfolding. In the middle of a complex, uncertain situation affecting many people, Facebook became a place where people were sharing information and looking to understand the condition of their loved ones."

This activation will change our policy around Safety Check and when we activate it for other serious and tragic incidents in the future. We want this tool to be available whenever and wherever it can help."

For Facebook Israel's top staff, Adi Sofer-Te'eni and Ro'i Tiger – the heads of Israeli market affairs and of research and development, respectively – Safety Check is part of the company's commitment to using the Internet for good.

"It's a concept that Mark (Facebook CEO Zuckerberg) has talked about. For us, it's a great thing to be able to get up in the morning and not only do a challenging job, but one we know is helping people around the world," said Tiger. "Facebook has become like a public square, used by over a billion people, so being able to leverage the platform to enable people to receive reassurance that their loved ones are safe is something we are very proud to be a part of.