#JeSuisJuif began trending shortly after it was revealed a second siege was unfolding at a Jewish supermarket in Paris.
At least three people are reported to have been killed after a gunman linked to the Charlie Hebdo murders and suspected of shooting dead a policewoman, took six people, including children, hostage.
The Associated Press reports police have ordered all shops to be closed in the neighbourhood.
The Board of Deputies of British Jews on Friday issued a statement in response to the latest incident.
According to the Jewish Year Book, there are 380,000 Jewish people in Paris.
Last year, a record 3,270 French Jews emigrated to Israel — a 63% percent hike from 2012. The Jewish Agency, which promotes emigration to Israel from the Jewish diaspora, estimates that figure could spike to 5,000.