WARSAW, Poland (AP) — With wreath-laying ceremonies and prayers, Poland on Monday observed the seventh anniversary of a plane crash in Russia that killed President Lech Kaczynski, the first lady and 94 others.

Poland's current Law and Justice ruling party is led by Kaczynski's twin brother, Jaroslaw Kaczynski, who has led regular commemorations for one of the nation's worst tragedies.

Kaczynski has suggested the crash could have been the result of foul play by Russia, and by Poland's own government at the time, which was led by his arch-rival, Donald Tusk. Kaczynski has questioned experts' conclusions that the crash was an accident, fueling a host a conspiracy theories. A special government commission re-investigating the crash is to present its findings later Monday.

Earlier, President Andrzej Duda and Marta Kaczynska, the late presidential couple's daughter, laid flowers at their marble tomb in the royal vaults of Wawel Cathedral in Krakow, in the south.

Jaroslaw Kaczynski placed a wreath in the national white-and-red colors at Warsaw's presidential palace shortly after 08:41 a.m., the time when the plane crashed on April 10, 2010, in the Russian city of Smolensk. The gathered crowd said prayers with him.

President Kaczynski and a wide-ranging delegation of Poland's political and military elite had been flying to Russia to pay tribute to some 22,000 Polish officers killed in the forest of Katyn and at other locations by the Soviet secret police during World War II.

Those circumstances have added to Poland's sense of continuous suffering due to Russia, and fueled conspiracy theories about the plane crash.