Poles have protested outside the Russian Embassy in Warsaw, claiming the plane crash two years ago that killed Polish President Lech Kaczynski and 95 others was an assassination.
Protesters burned an effigy of Russian Prime Minister Vladimir Putin.
The protest in the Polish capital came on the eve of the anniversary of the April 10, 2010, tragedy.
Protesters say they do not believe the crash was an accident, contradicting the conclusions of probes by Russian aviation authorities and Poland's government commission.
Many of the protesters were supporters of Jaroslaw Kaczynski, the dead president's twin brother, who has been fueling assassination theories.
Supporters of Jaroslaw Kaczynski, who leads the opposition nationalist Law and
Justice party, also protested in front of Prime Minister Donald Tusk's and President Bronislaw Komorowski's offices.
Poland's top prosecutor, General Andrzej Seremet, last month dismissed talk of an assassination. Seremet, who is overseeing the Polish investigation, said in an interview on TVN24 that "we did not find any evidence that the cause of the crash was an assassination."
Polish and Russian reports have pointed to fog and pilot error as the main causes of the crash, which occurred at an airport near Smolensk, in western Russia.
Based on reporting by AP