Sirens wailed and church bells rang as an estimated 100,000 people gathered in the Polish capital to say goodbye to their former president.
Many filed into Warsaw's Pilsudski Square carrying red and white Polish flags with black ribbons to mourn President Lech Kaczynski, his wife and 94 other people, including many top officials, killed in last Saturday's plane crash in Russia.
Interim President Bronislaw Komorowski told the crowd that with the accident, their world came "crashing down."
Mr. Kaczynski and his wife will be buried Sunday after a state funeral in Krakow. Dozens of world leaders had been planning to attend, but some have canceled their trips due to the ash cloud covering much of northern Europe.
Mr. Kaczynski had been traveling to a memorial service honoring 22,000 Polish military officers and others executed by the Soviets in the Katyn forest in World War Two.
Saturday's memorial service included a Catholic mass, hymns and a military gun salute. It will be followed by an overnight vigil for Mr. Kaczynski and his wife.
VOA's Sonja Pace, in Warsaw, said the crowd included people from across the country and from all parts of Polish society, from trade unionists to school children.
Many Poles said this is a sad time but that the tragedy has helped to bring people together as they say goodbye to the president for a final time.
In addition to Mr. Kaczynski, last Saturday's crash near Smolensk, Russia also killed the chief of Poland's armed forces, the director of the central bank and the deputy foreign minister.
Others who perished include 90-year-old Ryszard Kaczorowski, who was the last president-in-exile while Poland was under communism, and iconic labor leader Anna Walentynowicz.
Walentynowicz's firing from a job as a crane operator in Gdansk in 1980 touched off the strike that led to the founding of the Solidarity trade union and the eventual unraveling of communism in Poland. She was 80.
Interim President Komorowski says the date for Poland's presidential election will be announced next week.
Pope John Paul celebrated a mass in Pilsudski Square during his first pilgrimage to Poland as pope in 1979.
Some information for this report was provided by AP and Reuters.