World leaders observed a minute of silence for the victims of the Paris attacks
Dozens of world leaders linked arms as they began a historic march in Paris on Sunday, observing a minute of silence for victims of this week's attacks in the French capital.
President Francois Hollande linked arms with German Chancellor Angela Merkel and other leaders at the march including Israeli Prime Minister Benjamin Netanyahu and Palestinian president Mahmoud Abbas.
The king and queen of Jordan are in attendance and US President Barack Obama is represented by Attorney General Eric Holder.
Early estimates said over 600,000 people took part in rallies outside Paris in France on Sunday.
In Paris organisers said more than one and a half million people joined the rally and amateur video from the French capital showed huge crowds filling the streets.
Prior to the rally interior ministers from a range of nations gathered in the French capital and said it was "essential" for Internet companies to cooperate in tackling “terrorism”.
"We forcefully noted the need for greater cooperation with Internet companies to guarantee the reporting and removal of illegal content, particularly content that makes apologies for terrorism or promotes violence or hate," said French Interior Minister Bernard Cazeneuve.
Sunday's march in Paris began at the Place de la Republique in central Paris.
French President Francois Hollande said "today, Paris is the capital of the world."
"The entire country will rise up," he told ministers.
Those in attendance told AFP they were taking part in the demonstration as an act of defiance.
"I want to show that we're not scared of the extremists. I want to defend freedom of expression," said 70-year-old Jacqueline Saad-Rouana.
Another woman in her 50s who declined to be named said she was attending the march as it is "the way to show that I live in a country where everyone has their place."
The families of those who died in the three blood-soaked days that shook France to its core will rub shoulders with royalty and heads of state within an iron ring of security.
Defences were beefed up in a jittery Paris, with thousands of extra troops and police deployed to guard the march and snipers positioned along the route.
In a foretaste of the demonstration, more than 700,000 people poured onto the streets of cities across France on Saturday, many carrying banners reading "Je suis Charlie" and pens, symbolising their anger at the attacks.
The three-day rampage by three gunmen, who claimed to be members of the Al-Qaeda in the Arabian Peninsula (AQAP) and Islamic State (IS) groups, was followed by a chilling new threat from the Yemen-based AQAP.
AQAP top sharia official Harith al-Nadhari warned France to "stop your aggression against the Muslims" or face further attacks, in comments released by the SITE monitoring group.
German newspaper Bild said the bloodshed in France could signal the start of a wave of attacks in Europe, citing communications by IS leaders intercepted by US intelligence.
It said the US National Security Agency had intercepted communications in which leaders of the militant group announced the next wave of attacks, the newspaper said in its Sunday edition, citing unnamed sources in the US intelligence services.