Reuters has reported this only 10 minutes ago:
Polish President Lech Kaczynski was aboard.
Eighty-seven people died when a plane flying from Warsaw crashed near its intended destination in the Russian city of Smolensk, Itar-Tass news agency reported on Saturday, citing the Russian Emergencies Ministry.
The plane was headed to Smolensk, about half way between Poland and Moscow. There was no immediate word on whether President Kaczyski was dead. There is also no information as of yet on the cause of the crash.
I will update as new info comes in.
UPDATE: The BBC reports here that President Kaczynski and his wife were apparently both killed, along with several other high ranking officials.
UPDATE: Here is the report from Polish Radio.
The President was headed to Russia for a commemoration of the 70th anniversary of the Katyn Massacre of 1940, when Stalin's secret police murdered thousands of Polish officers.
UPDATE: Here is a video (narrated in Russian) about the crash. The scene is pretty awful, to say the least. My Russian is very, very rusty, so I can't translate most of it. The lead caption simply says that the Polish President's airplane has crashed in Smolensk Oblast (a political division). I thought it would be appropriate to add this very grim footage to the diary, regardless of language.