World Leaders Join Thousands Gathered In Paris For A Unity Rally After Three Days Of Terror That Left 17 People Dead.

Dignitaries and world leaders joined hundreds of thousands of people in Paris on Sunday in what government officials called a "unity rally" in defiance of a terrorism rampage that claimed 17 lives.

French President Francois Hollande was joined by other heads of state and dignitaries -- several who linked arms.

At the very front of the march was Dalil Boubakeur, the rector of the Great Mosque of Paris and president of the French Council of the Muslim Faith.

Though the march began at 3 p.m., the peaceful crowd swelled in size as night fell.

A man in the crowd said the French people must not "give in to fear." Terrorists, he said, "will not win."

Others carried signs that echoed the now-famous phrase that honored slain journalists at the magazine Charlie Hebdo, "Je suis Charlie."

"We are all cops."

"We are all Muslims."

"We are all French."