“At landing the presidential plane didn’t make it to the runway. Preliminary information has it that the plane became caught on the tops of the trees, crashed and disintegrated. There are no survivors of this crash,” Antufyev said.

During an official address Polish Prime Minister Donald Tusk named the crash “the most tragic non-military event in the history of Poland”

“The whole world has not seen such a drama,” he said.

In Warsaw people are bringing flowers to the Presidential Palace to pay their respects to late President.

A seven-day period of mourning has been announced in Poland to honor the victims of the crash. The government of Poland has also declared two-minutes of silence at noon (2pm Moscow time) on Sunday to honor those who died in Saturday’s plane crash near Smolensk.

Monday, April 12th has been an announced the day of mourning in Russia.

Bronislaw Komorowski, Marshal of the Sejm of Poland, has assumed the title of Acting President. According to the constitution, he has two weeks to announce the date of presidential elections.

Cause of crash: theories

Bad weather, human error and mechanical fault are considered as possible reasons behind the crash, Russia’s investigative committee reports. The plane was piloted by a Polish crew from the presidential air unit.

The Polish presidential aircraft, a Tupolev-154, was attempting to land at Severny airport in Smolensk in thick fog, a Russian investigative committee reports. It crashed 300-400 meters off the landing path.

The pilot had ignored warnings not to land the TU-154 plane in foggy conditions and made four attempts to land before crashing. Air traffic control in Belarus had apparently warned the captain to land in Minsk.

“In the morning the weather conditions at Smolensk ‘Severny’ airport were difficult, and fog was expected. The crew of the Polish Tu-154 with the Polish President on board was informed of the weather and advised to divert to a different airport due to the worsening weather conditions. However, the crew decided to land, which does not violate international practices since the final decision is made by the captain. The air traffic control officer issued several orders to divert, but the plane continued its descent. Unfortunately, this ended in tragedy,” said Russian Air Force Deputy Chief of General Staff, Lt. Gen. Aleksandr Alyoshin.

Leonid Koshelev, head of the Russian National Association of Business Aviation, says the pressure placed on the crew could have compromised the safety of the flight.

“There has been too much pressure on everybody having to do with this flight – on passengers, on the crew, on people on the ground. This pressure actually led to a tragedy. This is a lesson, that we should probably never let political and historic emotions take priority over flight safety.”

Lech Kaczynski with his wife (AFP Photo / Janek Skarzynski / Files)

Other suspected reasons behind the crash include the incompatibility of the plane’s landing system with the airports', and even overall poor technical condition of Polish authorities’ aircrafts.

Russia and Poland unite to investigate air tragedy

Russia’s President Dmitry Medvedev expressed deepest condolences to the people of Poland on behalf of the Russian people

Medvedev has set up a state commission, headed by Prime Minister Vladimir Putin, to investigate the accident.

Russia’s Foreign Minister Sergey Lavrov promised that everything will be done to “resolve all the issues as soon as possible”.

“A tragedy happened. Russia’s President and the head of the Government have been speaking to Polish Prime Minister Donald Tusk expressing our condolences to him and all the Polish people and the relatives of those who died,” Lavrov said.

Russian Emergencies Minister Sergey Shoigu and Russian Transport Minister Igor Levitin also went to the crash site.

“There is no doubt that Russia and Poland will continue co-operating on the investigation of all the circumstances of this tragedy,” Dmitry Rogozin, Russia’s envoy to NATO assured.

Russian State Duma Deputy Vladimir Pligin says the investigation will involve all possible measures and will be transparent.

“No doubt the investigation will not be a top-secret investigation. It’s a big tragedy for both the people of Poland and the people of Russia, and all of us are interested in an open and professional investigation.”

The head of the foreign affairs committee of the Russian Federation Council, Mikhail Margelov, also believes the investigation into the crash will be thorough and open.

“I think the combined efforts could only bring us to the truth about what really happened this morning near the city of Smolensk,” he said.

Meanwhile Poland will conduct its own investigation into the accident independently from Russia, the Polish Prosecutor General said.