The body of Polish President Lech Kaczynski - who died along with 95 others when their plane crashed in Russia - has arrived back in Warsaw.
It was driven through crowd-lined streets to the presidential palace, where it will lie in state for a week.
The president, military chiefs and MPs were due to attend a memorial for a World War II massacre when their plane crashed near Smolensk on Saturday.
Russian officials say the pilots were warned that they were flying too low.
Russian Prime Minister Vladimir Putin earlier attended a memorial service for the victims at the crash site, near the city of Smolensk.
He has said he would personally oversee the investigation into the disaster, promising to find out what happened as soon as possible.
Week of mourning
No-one survived Saturday's crash, and acting Polish President Bronislaw Komorowski has called for a week's mourning for the dead.
He, Prime Minister Donald Tusk and the president's twin brother, Jaroslaw, were among the dignitaries to receive Mr Kaczynski's coffin at a military airport in Warsaw after its repatriation from Smolensk.
The casket, draped in the red-and-white Polish flag, was carried across the tarmac by soldiers and placed before Catholic clerics who led a short prayer service before mourners took turns to kneel before the coffin and pay their respects.
Crowds of Poles lined the streets of the city, standing silently as the president's body was driven under military escort to the presidential palace, where it will be available for public viewing.
Thousands had gathered in front of the building, carrying flowers, candles, Polish flags and portraits of the deceased.
Some wept, others stood in silent reflection. As the president's body arrived, they softly began to sing the Polish national anthem.
Church services to honour their memory were earlier held across the country, as was a two-minute tribute, with church bells and police sirens.
'A great patriot'
Jaroslaw Kaczynski, Poland's former prime minister, had earlier travelled to Russia to help identify his twin's body.
The brothers' strong nationalist, conservative agenda divided opinion in Poland, but the BBC's Adam Easton in Warsaw says the president's supporters and opponents have joined together in paying tribute to him.
Boguslaw Staron, a 70-year-old from Warsaw, described Mr Kaczynski as "a great patriot".
"He taught Poles how to respect our traditions, how to fight for our dignity, and he made his sacrifice there at that tragic place," he said.
Poles gathered in town squares and in the streets at midday (1000 GMT) and stood silently to mark the tragedy, as church bells rang and emergency sirens wailed around them.
The president had been flying to Russia along with his wife, the heads of the army and navy, MPs and senior historians to mark 70 years since Soviet forces massacred more than 20,000 Poles near Katyn.
Controversial figure
Russia has declared Monday a day of mourning and Russian Prime Minister Vladimir Putin, who visited the crash site with Polish counterpart Donald Tusk, said he would oversee the inquiry.
Russian and Polish investigators have recovered the flight-data recorders and are carrying out a joint inquiry.
They are looking into the possibility that pilots ignored warnings that they were approaching Smolensk too low.
Experts have also suggested that the age and condition of the Polish president's Soviet-era Tupolev 154 plane could have played a part in the accident.
Correspondents say the plane was flying too low and clipped some trees as it approached the runway in thick fog, before it came down in a forest.
A Russian general said air traffic controllers had repeatedly urged the pilots to pull up.
Investigators from the Russian emergencies ministry are sifting through the debris but say there was no evidence of mechanical failure.
Mr Kaczynski was a controversial figure in Polish politics.
He was active in the Solidarity movement that helped bring an end to Communist rule, but later fell out with Solidarity leader Lech Walesa.
He advocated traditional Catholic values, opposed rapid free-market reforms and favoured retaining social welfare programmes.
As president, he held fewer powers than the prime minister but retained a significant say in foreign policy. He could veto new laws and frequently blocked government reforms.
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