Poland's President Lech Kaczynski, its central bank head and the country's military chief were among 96 people killed when their plane crashed in thick fog on its approach to a Russian airport this morning.
The president's wife and several other high-ranking government officials were also aboard the aged Tupolev Tu-154, which plunged into a forest about 2 km from the airport in the western Russian city of Smolensk.
Polish Prime Minister Donald Tusk described the crash as "the most tragic event of the country's post-war history". Tusk, ashen-faced and wearing a black suit and tie, told a news conference he would fly to the crash site and he has called an emergency cabinet meeting to discuss the tragedy.
The Polish foreign ministry said this afternoon that the cause of the accident was not yet clear. Radio reports said the president's plane, a Tupolev Tu-154 was recently overhauled.
Eye witnesses in Smolensk say the airport was cloaked in thick fog at the time of the crash.
"The plane was landing in poor visibility," said Andrei Yevseyenkov, spokesman for the region, to Russian television. "Air traffic controllers suggested the plane divert to Minsk but the pilots took their own landing decision."
According to Russian media reports, the plane's left wing brushed trees, the fuselage caught fire and the plane crashed a kilometre from the runway.
Russia's Emergencies Ministry said 96 people were aboard the government plane, including the 88 members of a Polish delegation en route to commemorate Poles killed in mass murders in the town of Katyn under orders from Soviet leader Josef Stalin in 1940.
A Russian mission control official who had been present during conversations with the pilot said he had ignored advice.
"The pilot was advised to fly to Moscow or Minsk because of heavy fog, but he still decided to land. No one should have been landing in that fog," he said, on condition his name was not published.
Polish Justice Minister Krzysztof Kwiatkowski said he would order a special inquiry into the crash.
The death of Mr Kaczynski, who with his twin brother was a dominant force in Polish politics, brings political uncertainty. A presidential election had been due in October but now must be held within two months, according to the constitution.
On the death of the president, Poland's constitution promotes the parliamentary speaker to acting head of state until a new president is elected
In a twist of fate, this role now falls to Bronislaw Komorowski, the man recently nominated by Mr Tusk's Civic Platform to challenge Mr Kaczynski in the presidential election later this year.
The third candidate in the election, Jerzy Smajdzinski of the Democratic Left Alliance, also perished in the crash. Mr Kmorowsko has announced a week-long period of mourning.
"The political consequences will be long-term and possibly will change the entire future landscape of Polish politics," said Jacek Wasilewski, professor at the Higher School of Social Psychology in Warsaw.
Mr Kaczynski, 60, was a one-time ally of Solidarity hero Lech Walesa and a co-founder of the rightist Law and Justice party with his brother. He resigned from the party when he became president in 2005 but continued to support it.
Some relatives of victims of the Katyn massacres were also on board the plane, said a Polish government official in Smolensk.
Thousands of Polish prisoners of war and intellectuals were murdered at Katyn by Soviet forces in spring 1940 in an enduring symbol for Poles of their suffering under Soviet rule.
Additional reporting agencies.
