WARSAW - Draped in a red and white Polish flag, the body of Lech Kaczynski was ceremoniously returned to Warsaw, as millions turned out to mourn the head of state and 95 other victims of a plane crash.

The plane carrying the 60-year-old President, his wife and senior religious, political and military figures crashed and exploded while trying to land in thick fog in western Russia on Saturday morning local time. Everyone on board was killed.

The party had been travelling to a ceremony at the site of the Katyn massacre, in which the Soviet secret police executed thousands of members of Poland's professional and officer classes in 1940.

The crash killed a major and significant section of the country's governing elite in a single and shocking blow to Poland. Donald Tusk, Poland's Prime Minister, who reportedly burst into tears when informed, described the incident as "The worst national political tragedy Poland has experienced since the Second World War."

Some 30 hours after the crash, a military plane bearing the late President's body arrived at Warsaw's main airport; waiting to receive it were Mr Tusk and President Kaczynski's twin brother, the former conservative prime minister, Jaroslaw Kaczynski. The President's daughter, Marta, knelt before her father's coffin sobbing and pressing her forehead against its side.

The coffin was then carried by a squad of Polish soldiers marching in slow time to a waiting hearse, and was driven to the capital's presidential palace. The President's body is expected to lie in state for several days before a full state funeral is held.

Tens of thousands of Warsaw residents lined the roads from the airport to the city centre to pay tribute as the coffin passed with its motorcycle police escort. The stunned nation is observing a week of national mourning. This began with two minutes silence yesterday, after which church bells rang out and air-raid sirens wailed eerily across the country.

The presidential palace rapidly turned into a shrine for the crash victims. A sea of candles in glass holders and thousands of red and white flowers covered the pavements in front of the building. Traffic was brought to a standstill as hundreds carrying roses and candles joined a long queue to sign a book of condolences inside the palace.

Millions attended special Sunday Masses to mourn the dead throughout Poland. In Krakow, an ancient church bell that is only rung on occasions of national disaster pealed out across the rooftops as thousands turned out in the pouring rain. Many compared the occasion to mourning ceremonies held in Poland following the death of the Polish Pope John Paul II in April 2005.

Kaczynski was founder of Poland's controversial nationalist and conservative Law and Justice Party. A former adviser to the once-banned Solidarity trade union and a champion of traditional Polish values, he was lauded by conservatives but disliked by Polish liberals. During his tenure Poland's relations with its EU neighbours and its erstwhile enemies, Germany and Russia, were for the most part strained.

"He taught Poles how to respect our traditions and how to fight for our dignity," said Bogulsav Staron, 70, who was one of the mourners outside the palace. "He made his sacrifice, there at that tragic place," he added.

"I didn't much like the President's politics, I was no fan of his, but I have come here to mourn anyway. This is too big a tragedy to ignore," said another man who stood outside the palace with a candle in his hand.

Political implications

The crash has left a gaping hole in Poland's military, political and religious establishment. The 96 killed included two bishops, the chiefs of staff of both the Polish army and navy, the head of the president's chancellery, the head of the Olympic Committee, the country's human rights commissioner and the central bank president.

Officials in Warsaw made efforts to assure the public that the armed forces and the government would continue to function, with acting heads named for the military services as well as for the central bank.

However it was still not clear what political implications the crash would have. Under the Polish constitution, President Kaczynski's role has been temporarily assumed by the speaker of parliament, Bronislaw Komorowski. As Acting President, he has declared that he will announce a date for a presidential election to be held within 14 days. Polling would then have to take place within the following 60 days.

The late President's wife, Maria Kaczynska, was also killed in the plane crash, as was 80-year-old Anna Walentynowicz, the former Gdansk shipyard worker whose sacking in 1980 led to the formation of the Solidarity union, which eventually overthrew Polish Communism.

Lech Walesa, the former Solidarity leader, Nobel Peace Prize winner and former Polish president signed a book of condolences in his home in Gdansk: "The elite of our country has perished. This is the second disaster after Katyn," he said. Among the dead were some relatives of the estimated 22,000 Polish officers and other professionals executed by Stalin's secret police at Katyn and other sites in the region.

The tragic irony of the accident occurring almost exactly 70 years after that massacre was not lost on leading Polish figures. Former president Alexander Kwasniewski said: "This is a wound that will be very difficult to heal."

Cause of crash

The Tu-154 that crashed was 26 years old. It was overhauled in December in Russia, with Russian experts yesterday insisting it was airworthy and blaming pilot error and bad weather.

Russian officials said the airport, 434km west of Moscow, had been closed because of thick fog.

They advised the pilot to land instead in Moscow or Minsk. But he continued with the original flight plan - making three abortive attempts to land.

On the fourth attempt, the Russian-built airliner crashed. According to witnesses, Kaczynski's plane was 20m off the ground when it ploughed into the trees.

The Smolensk airfield is not equipped with an instrument landing system to guide planes to the ground.

Although there was no suspicion of foul play, the timing and location of the disaster - together with Kaczynski's known antipathy towards the Kremlin - are likely to fuel conspiracy theories.

"We still cannot fully understand the scope of this tragedy and what it means for us in the future. Nothing like this has ever happened in Poland," Russia's Foreign Ministry spokesman, Piotr Paszkowski, said.

Russian Prime Minister Vladimir Putin personally took charge of the investigation and very quickly and publicly offered condolences, along with Russian President Dmitry Medvedev.

"On this difficult day the people of Russia stand with the Polish people," Medvedev said.

Other world leaders yesterday paid tribute to Kaczynski, who was elected in 2005. He and his twin brother, Jaroslaw, a former Prime Minister now in opposition, emerged from Poland's anti-communist Solidarity movement.

Among the fallen:

* President Lech Kaczynski and his wife, Maria.

* Poland's Deputy Foreign Minister, Deputy Parliament Speaker, 12 members of Parliament.

* The head of the national bank, head of the National Security Office, Olympic Committee head, civil rights commissioner and at least two presidential aides.

* The Army chief of staff, the Navy's chief commander and heads of the air and land forces, Army chaplain.

* Some on board were relatives of the officers slain in the Katyn massacre in World War II.

* Among the victims was Anna Walentynowicz, whose firing in August 1980 from the Lenin Shipyards in Gdansk sparked a workers' strike that spurred the eventual creation of the Solidarity freedom movement.