Yohan Cohen
Yohan Cohen Screenshot/Facebook

Details are emerging of the bloody attack on a kosher supermarket Friday in which four shoppers were murdered, as France struggles to come to terms with the string of attacks of recent days.

Yoav Hattab, Philippe Braham, Yohan Cohen and Francois-Michel Saada were all killed by Muslim extremist Amedy Coulibaly, who took terrified shoppers hostage in a Jewish supermarket as many of them were carrying out last-minute Shabbat preparations.

According to reports, one of the hostages - apparently Yohan Cohen - attempted to disarm Coulibaly as he burst into the store, in an incredible act of heroism. But after a brief struggle in which he failed to snatch the terrorist's gun, he was shot in the head, becoming Coulibaly's first victim.

Plans are underway for all four of Friday's victims to be buried in a state ceremony in Israel.

Police are still searching for Coulibaly's 26-year-old partner Hayat Boumeddiene, who they are describing as "armed and dangerous." Coulibaly himself was killed when French commandos stormed the shop and caught him off-guard as he bent down to pray.

Boumeddiene is suspected of being involved in a shooting attack Thursday in Paris, in which a policewoman was killed and another person seriously injured.

That attack came just a day after the deadly assault by two other Islamist terrorists on the central Paris offices of the satirical magazine Charlie Hebdo, which left 12 dead and 11 more wounded.

French authorities have dramatically ramped-up security, with the defense ministry announcing the deployment of an additional 500 troops to the greater Paris area, adding to the 850 soldiers already deployed after previous attacks left France on high alert.

Meanwhile, more than 200,000 people have poured onto the streets in cities across France in poignantly silent marches paying tribute to those killed in the nation's bloodiest week in more than half a century.

In Paris, mourners lay flowers at the scene of Friday's killings as a tribute, and one woman attached signs to a police barrier reading: "Je suis Charlie" ("I am Charlie"), "I am police", "I am mourning", "I am Jewish."

It is just a taste of what was to come in Paris Sunday, where a major rally will be held for national unity, to be attended by President Francois Hollande and a host of world leaders.