Tens of thousands of Poles sang the national anthem and tossed flowers at the hearse carrying the body of President Lech Kaczynski through the streets of Warsaw Sunday, one day after he and dozens of political, military and religious leaders were killed in a plane crash.

Kaczynski's body was transported from Russia Sunday morning, to be met by an honour guard and rows of dignitaries.

When his coffin emerged, guarded by four Polish troopers bearing sabers, Kaczynski's daughter Marta knelt before it and rested her forehead on the coffin.

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

The coffin was placed aboard a Mercedes-Benz hearse for the 12-kilometre journey to the presidential palace, watched by thousands of Poles, many of them weeping openly.

In Warsaw's historic centre, large sections of the street were blocked to traffic to allow the flow of people expressing their grief. Mourners carried candles and roses and joined a long line to sign a book of condolences in the palace.

Earlier, the country held two minutes of silence in memorial for those killed in the crash.

Church bells pealed at noon and emergency sirens wailed for nearly a minute before quieting.

As the din faded into silence, hundreds of people in front of the presidential palace stopped what they were doing, some bowing their heads and closing their eyes to mark the moment. Buses and trams halted in the streets.

Magdalena Jensen, a journalist with Polish Radio in Warsaw, said the two minutes of silence completely enveloped the country.

"Everything, the entire nation, was asked to be silenced, from radios to the general people on the streets," Jensen told CTV News Channel in a telephone interview Sunday morning.

"It's just something people are making part of their day."

No date for a funeral has been set and the presidential palace has not yet said if Kaczynski will lie in state.

The death of the president and much of the state and defence establishment in Russia, en route to commemorating one of the saddest events in the neighbouring countries' long, complicated history, was laden with tragic irony.

Kaczynski and 95 other officials had been heading to Smolensk on Saturday to honour 22,000 Polish officers slain by the Soviet secret police in 1940.

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

Among the dead were the national bank president, the 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. Government spokesman Pawel Gras said the country's armed forces and state offices were operating normally despite the devastating losses.

Michal Boni, an official in the prime minister's office, said they remained in constant contact with the deputy head of the National Bank of Poland, Piotr Wiesiolek.

He said the bank's Monetary Policy Council will hold a meeting Monday, as previously planned.

"We are prepared to take various decisions, but we do not see that anything dangerous could happen in the economy," Boni said.

Elections

The acting president, Parliament Speaker Bronislaw Komorowski, said he would call for early elections within 14 days, in line with the constitution. The vote must be held within another 60 days.

In Moscow, Russia's Transport Ministry said that Russian and Polish investigators had begun to decipher flight data recorders of the aging Soviet-built Tu-154 airliner that crashed while trying to land in deep fog in Smolensk.

The Polish presidential plane was completely overhauled in December, and speculation about the cause of the crash has focused on some kind of human error.

The Smolensk regional government said Russian dispatchers had asked the Polish crew to divert from the military airport there because of the fog and land instead in Moscow or Minsk, the capital of neighbouring Belarus.

Former president, Solidarity founder and Nobel Peace Prize laureate Lech Walesa, said it was too soon to cast blame.

"Someone must have been taking decisions on that plane. I don't believe that the pilot took decisions single-handedly," he told reporters. "That's not possible. I have flown a lot and whenever there were doubts, they always came to the leaders and asked for a decision, and based on that, pilots took decisions. Sometimes the decision was against the leader's instructions."

Kaczynski, 60, was the first serving Polish leader to die since exiled Second World War-era leader general Wladyslaw Sikorski was killed in a mysterious plane crash off Gibraltar in 1943.

With files from The Associated Press