Huge crowds and some 40 world leaders are expected in Paris for a unity march in the French capital after three days of terror left saw 17 people killed, reports the BBC.
The rally is expected to dwarf marches across France on Saturday that saw 700,000 people take to the streets.
About 2,000 police officers and 1,350 soldiers are being deployed in Paris to protect more than a million marchers.
Police are seeking accomplices of the gunmen who attacked satirical magazine Charlie Hebdo and a kosher supermarket.
Eleven people were killed at the magazine offices on Wednesday, with a policeman shot dead nearby. Four hostages died at the supermarket on Friday.
At the Elysée Palace ahead of Sunday's march, President François Hollande met leaders from the Jewish community, which is still in shock after gunman Amedy Coulibaly attacked the Hyper Cacher store in eastern Paris.
He is also believed to have shot dead a policewoman on Thursday.
He died at the scene but his partner, Hayat Boumeddiene, is still wanted by police - though she is thought to have fled France last week.
Officials believe she may have entered Turkey en route to Syria.
The interior minister says France will stay on high alert in the coming weeks.
Bernard Cazeneuve will host a meeting on Sunday morning of fellow interior ministers from across Europe, including the UK's Theresa May, to discuss the threat posed by militants.
Mr Cazeneuve promised "exceptional measures" for the massive unity march in Paris on Sunday, including positioning snipers on roofs.
The foreign leaders expected to attend the rally include UK prime minister David Cameron, German chancellor Angela Merkel, Palestinian leader Mahmoud Abbas and Israeli prime minister Benjamin Netanyahu.
The march, which will be led by relatives of the victims of last week's attacks, will leave Place de la République at 15:00 local time (14:00 GMT).