The country's President Lech Kaczynski and 95 others died in the crash.
ADVERTISEMENTPolish officials have reiterated claims that Russia was behind a 2010 plane crash that killed the country's president.
A special government commission has once again alleged that the accident was a result of an assassination plan by Moscow.
Two separate reports by Polish and Russian experts have concluded that the aircraft crashed due to human error amid dense fog.
The Soviet-made Tupolev Tu-154 Polish air force plane went down on its approach to the Russian Smolensk airbase on 10 April 2010.
President Lech Kaczynski, Poland's first lady and 94 others -- including senior military officers, and 18 members of the Polish Parliament -- died in the crash, on their way to the 70th anniversary of the Katyn massacre.
In the latest Polish report -- released 12 years after the disaster -- Russia has been accused of detonating two planted "explosives" in the plane.
The death of Kaczynski was the result of an “act of unlawful interference by the Russian side,” the commission’s head Antoni Macierewicz told a news conference on Monday.
“The main and indisputable proof of the interference was an explosion in the left wing... followed by an explosion in the plane’s centre,” he added.
Macierewicz -- a former defence minister -- denied that any mistakes were made by the Polish pilots or crew members, despite poor weather conditions at the time of the crash.
The latest report repeats many previous allegations made by the commission, appointed by Jaroslaw Kaczynski, the twin of the late president.
Jaroslaw Kaczynski currently serves as Poland's deputy prime minister and leader of the ruling conservative Law and Justice party and has always claimed that his brother's plane crashed due to "sabotage".
Suspicions are additionally fuelled by Russia’s refusal to return the wreckage, which has complicated Poland’s investigation.
Kaczynski also accused former Polish Prime Minister Donald Tusk of covering up the events.
The latest allegations come amid heightened tensions between Warsaw and Moscow following Russia's invasion of Ukraine.