PARIS RALLY AGAINST TERRORISM

[Stephan Bobb]

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

He lifted his arm and gestured to many people around him who came to denounce violence: "We are all Muslim!"

French officials announced "exceptional measures" to protect the throngs gathered near the Place de la Republique in central Paris, and a who's who of foreign leaders at the rally -- a test of the security forces of a nation rocked by days of terrorist violence.

Interior Minister Bernard Cazeneuve has outlined extraordinary security measures to protect VIPs such as British Prime Minister David Cameron, German Chancellor Angela Merkel and Spanish Prime Minister Mariano Rajoy.

At many moments, the gathering looked like a funeral. Merkel was photographed leaning her head gently on Hollande's shoulder

After the rally, Hollande arrived to huge applause and a cheering crowd at the Synagogue de la Victoire to show support for France's Jews. He was joined by Israeli Prime Minister Benjamin Netanyahu.

The targeting of the kosher grocery store shook the nation's Jewish communities. Amid heightened security concerns, the synagogue was closed Saturday for the first time since World War II.

On Sunday, "Jerusalem of Gold" -- a popular song by Naomi Shemer that became an anthem during the Six-Day War in 1967 -- played in the place of worship

World leaders -- but no Obama

It was just one of several gestures of solidarity Sunday among some of the world's most influential leaders.

Russian Foreign Minister Sergey Lavrov, Turkish Prime Minister Ahmet Davutoglu, and Jordan's King Abdullah II and Queen Rania were at the rally.

Even more rare and significant, Palestinian Authority President Mahmoud Abbas and Netanyahu both attended the event.

Several people in the crowd and on social media wondered why U.S. President Barack Obama was not there; he's at the White House on Sunday.

CNN has asked for an explanation from the State Department and White House of his absence. There has been no response so far.

Secretary of State John Kerry was not at the rally either.

A senior State Department official told CNN that Kerry had committed a long time ago to be the lead speaker at Indian Prime Minister Narendra Modi's entrepreneurship and innovation summit in India. The official said that Kerry did not want to cancel that as he continues to wok on the United States' relationship with the nation.

Attorney General Eric Holder was not at the rally but was in Paris this weekend to attend a security summit on combating terrorism. He recorded interviews that aired in the U.S. on Sunday.

Ambassador to France Jane Hartley represented the United States at the rally. She tweeted several images of the crowd.

Speaking on air with CNN's Jake Tapper, who was at the rally, "Global Public Square" host Fareed Zakaria tried to put Obama and other senior leaders' absence in context.

Zakaria called the absence of top officials a mistake.

France is the United States' "deepest ideological ally," he said, and it would have been a meaningful image to have a senior administration member, or the President, standing shoulder to shoulder with other leaders.

Tapper noted that security has been tenuous. Cazeneuve and other officials said 2,300 police officers, as well as paramilitary forces, would be deployed Sunday. The dignitaries and leaders were to be protected by special units.

Police snipers, plainclothes and anti-terror officers were deployed, and parking and transit restrictions were in place. The government planned to close large sections of the city to traffic, Cazeneuve said.

Zakaria observed that security concerns didn't dissuade Netanyahu or Abbas or other controvrsial leaders from showing up. The bright side, he said, is that Obama's absence showed that the struggle against radical Islam is "not all about America."

"Many people have tended to think that Islamic terrorism wouldn't exist without America," Zakaria said. "This is really a struggle between the civilized world and a band of extremists. Even if you take the U.S. out of it ... the civilized world is up in arms."

French investigators are still trying to piece connections between three terror suspects killed Friday and their suspected links to al Qaeda in the Arabian Peninsula and other terrorist groups. Security will remain heightened as the investigations continue, officials have said.

CNN's Kevin Bohn contributed to this report.