国际英语新闻：Polish president, 96 others killed in Russia plane crash

The deaths were not expected to directly affect the functioning of Polish government: Poland's president is commander in chief of its armed forces but the position's domestic duties are chiefly symbolic. Most top government ministers were not aboard the plane.

Sergei Antufiev, governor of the Smolensk region,told Russia-24 television news network that the plane "clipped the tops of the trees, crashed down and broke into pieces."

Russian television showed the plane's wreckage scattered in a forest with parts still on fire. The plane's two black boxes have been found and are being analyzed by Russian investigators.

Andrei Yevseyenkov, a spokesman for the Smolensk government, said Russian dispatchers asked the crew to divert from Smolensk and land instead in Minsk, the capital of neighboring Belarus, or in Moscow because of the fog.

People present flowers and light candles to mourn for the passed-away Polish President Lech Kaczynski in an air crash in front of the Polish Embassy in Brussels, capital of Belgium, April 10, 2010. All 97 people on board died when the Tu-154 aircraft carrying Kaczynski, his wife, and a delegation of senior officials crashed in thick fog while attempting to land at the Smolensk airport.

"The pilot was advised to land in Minsk, but decided to land in Smolensk," the spokesman said.

While traffic controllers generally have the final word in whether it is safe for a plane to land, they can and do leave it to the pilots' discretion.

A security source told the RIA Novosti news agency that human error was most likely to blame.

"A mistake by the crew during landing maneuvers has supposedly caused the crash," the source said.

The Interfax news agency cited the deputy head of Russian air force headquarters as saying air traffic controllers had advised the pilot not to land at the airport due to heavy fog, but the suggestion was ignored.