Lech Kaczynski, the president of Poland, died Saturday in plane crash in western Russia.
According to Russian officials, the plane crash also killed 96 other people, including Kaczynski's wife and other government officials.
CNN reported that the plane crashed as it was trying to land at an airport near the city of Smolensk.
The president had been traveling with a Polish delegation for the 70th anniversary Russian massacre of Polish prisoners of war.
The event was intended to ease relations between Poland and Russia.
Although Russian television portrayed Kaczynski in a mostly negative light Saturday, the country declared Saturday a day of mourning.
According to the UK's Mirror, the Polish government declared a week for national mourning.
People gathered outside the presidential palace to lay flowers and light candles.
Parliament Speaker Bronislaw Komorowski took over as acting president.
Kaczynski was 60 years old.