Millions of people were expected to join a march through Paris Sunday in solidarity with the victims of the Islamist attacks, with dozens of world leaders to attend the show of support for France.

French Prime Minister Manuel Valls predicted the massive turnout to honour the 17 killed in the attacks which targeted a satirical magazine, kosher supermarket and police.

“I have no doubt that millions of citizens will come to express their love of liberty, their love of fraternity,” he told thousands gathered Saturday near where a gunman killed four hostages at the supermarket.

France has deployed thousands of police and troops to beef up security ahead of the march, which follows rallies across France on Saturday which drew more than 700,000 in support of the victims of the three-day killing spree.

“The real battle is to defend freedom of thought,” said 40-year-old Yamina, tears in her eyes, at a rally in the southern city of Marseille.

A security force of around 2,200 will guard the route of Sunday’s march, which will run three kilometres (1.9 miles) from the historic Place de la Republique to Place de la Nation in the east of the capital, the interior minister said, with snipers stationed on rooftops.

Dozens of world leaders including British Prime Minister David Cameron, German Chancellor Angela Merkel and Israeli Prime Minister Benjamin Netanyahu were set to attend Sunday’s march.

Russian Foreign Minister Sergei Lavrov, Palestinian president Mahmud Abbas and the king and queen of Jordan are also among those set to take part.

Public transport will be free to ease access into and throughout Paris and international train operator Thalys said it was also cutting fares to the French capital on Sunday.

Far-right leader Marine Le Pen urged her supporters to attend rallies outside Paris, but not in the capital, denouncing the exclusion of her Front National party from preparations for the event.