WARSAW, Poland - Some 100,000 Poles filled Warsaw's biggest public square yesterday, joining together for a memorial and funeral Mass for the 96 people killed in a plane crash a week earlier.

The thickening cloud of volcanic ash over Europe caused some world leaders - including President Barack Obama, German Chancellor Angela Merkel and Canadian Prime Minister Stephen Harper - to cancel plans to attend Sunday's state funeral. Still, some European leaders said they would drive to Krakow.

Obama "waited as long as possible before he made the decision because he wanted to come," said Lee Feinstein, U.S. ambassador to Poland. "But it was impossible for him to travel."

The crowd in Warsaw's Pilsudski Square waved white-and-red Polish flags with black ribbons of mourning affixed to them. A massive white stage, a large cross in the center, was flanked by oversized photos of the dead, including President Lech Kaczynski.

The names of the dead were read aloud, starting with the president and his wife, Maria, while Marta, their only child, and Jaroslaw Kaczynski, the president's twin brother and former prime minister, looked on. Others at the service included former President Lech Walesa, Prime Minister Donald Tusk and acting president Bronislaw Komorowski.

"Our world went crashing down for the second time at the same place," Komorowski said of the crash near Russia's Katyn forest, site of a World War II massacre of Polish officers.

Tusk called the crash a calamitous event that was "the greatest tragedy in Poland since the war." The crash claimed the lives of a swath of Poland's elite, including numerous lawmakers, the central bank governor, the commanders of the country's armed forces and the head of its Olympic committee, among others.

The coffins bearing Kaczynski and his wife were taken to a Gothic cathedral in Warsaw for an evening Mass, carried on artillery caissons pulled by army Humvees escorted by Polish soldiers on foot and horse-riding cavalry behind them.

After the Mass, their bodies will remain in the cathedral and then flown early today to Krakow aboard a military transport for the state funeral, said presidential palace spokesman Jacek Sasin.

Among the mourners yesterday was Teresa Winkler, 76, who came to honor a president "who took care of the people forgotten by society," such as aging World War II soldiers and forgotten Solidarity activists.

"He was a real patriot and a real Pole," Winkler said. "I am afraid it will be hard to find another president like Kaczynski."

Nearby was a group of Chechen refugees who said they were there to honor the first lady for her charity work and efforts to help them.

Members of Solidarity, the freedom movement that Kaczynski supported and that still exists as a labor union, waved their banners.

The crash of the Tupolev 154 - which investigators have said was likely because of human error - plunged Poland into a deep grief not seen since the death of Pope John Paul II five years ago.

Latest videos