Poland's government moved swiftly Sunday to show that it was staying on course after the deaths of its president and dozens of political, military and religious leaders, even as tens of thousands of Poles expressed their grief over the plane crash in Russia that shocked the country.

New acting chiefs of the military were already in place and an interim director of the central bank was named Sunday, with work running as usual, said Pawel Gras, a government spokesman.

It was a rare positive note on a day wracked by grief for the 96 dead and laced with reminders of Poland's dark history with its powerful neighbor. The Saturday crash occurred in thick fog near the Katyn forest, where Josef Stalin's secret police in 1940 systematically executed thousands of Polish military officers in the western Soviet Union.

President Lech Kaczynski and those aboard the aging Soviet-built plane had been headed there to honor the dead. A preliminary analysis showed the plane had been working fine, a Russian investigator said.

Tens of thousands of Poles softly sang the national anthem and tossed flowers at the hearse carrying the 60-year-old Kaczynski's body Sunday to the presidential palace after it was returned from Russia's Smolensk airport, the site of the crash.

The coffin bearing the president's remains were met first by his daughter Marta, whose mother, the first lady, Maria Kaczynska, also perished in the crash. She knelt before it, her forehead resting on the coffin.

She was followed by Jaroslaw Kaczynski, the former prime minister, and the president's twin brother. He, too, knelt and pressed his head against the flag-draped coffin before rising slowly and crossing himself.

Standing sentinel were four Polish troopers bearing sabers. There was no sign of the twins' ailing mother Jadwiga, who has been hospitalized. The president had canceled several foreign trips lately to be by her side.

The coffin was placed aboard a Mercedes-Benz hearse and slowly traveled several miles to the palace, watched by thousands of weeping Poles.

"He taught Poles how to respect our traditions, how to fight for our dignity, and he made he made his sacrifice there at that tragic place," said mourner Boguslaw Staron, 70.

President Dmitry Medvedev declared Monday a day of mourning in Russia, and his country held two minutes of silence in memory of those killed in the crash.

Church bells pealed at noon and emergency sirens shrieked for nearly a minute before fading. Hundreds bowed their heads, eyes closed, in front of the presidential palace. Buses and trams halted in the streets.

No date for a funeral has been set and the Polish presidential palace has not yet said if Kaczynski will lie in state, though it is not a Polish tradition.

Kaczynski was the first serving Polish leader to die since exiled World War II-era leader Gen. Wladyslaw Sikorski was killed in a mysterious plane crash off Gibraltar in 1943.

Poland is a young democracy, adopting its constitution in 1997 after decades under communism, but political scientist Kazimierz Kik of Kielce University said he was confident it would remain stable.

"The democracy is passing the test, there is no doubt about it," he said. "This tragedy does not threaten the state in any measure, Poland's institutions are strong, but there is the trauma of the nation."

Among the dead were Poland's army chief of staff, the navy chief commander, and heads of the air and land forces. At the Field Cathedral of the Polish Army in Warsaw, hundreds gathered for a morning Mass and left flowers and written condolences.

Also aboard the aging Tu-154 plane were the national bank president, the deputy foreign minister, the army chaplain, the head of the National Security Office, the deputy parliament speaker, the Olympic Committee head, the civil rights commissioner and at least two presidential aides and three lawmakers.

Michal Boni, an official in the prime minister's office, said it remained in constant contact with the deputy head of the National Bank of Poland, Piotr Wiesiolek, who is acting director of the bank until a new one is appointed.