WARSAW, Poland — Polish president Lech Kaczynski, 60, was killed in an air crash near the Russian city of Smolensk on Saturday morning along with 95 other people, after the plane tried repeatedly to land in very foggy conditions.

The crash also killed Kaczynski's wife, Maria, the governor of the central bank, Slawomir Skrzypek, the heads of Poland's army, navy, air force and special forces, as well as many other senior politicians and dignitaries.

The delegation was on its way to memorial services in the Katyn forest, located about 10 miles from Smolensk, which was the site of the murder of more than 4,000 Polish officers by the Soviet Union in 1940.

“The modern world has never seen such a drama,” said a shaken Donald Tusk, the prime minister, who was to fly to Smolensk to meet with Vladimir Putin, his Russian counterpart. “Many of our friends and acquaintances have died.”

The country was in shock after the tragedy, with hundreds of people showing up at the presidential palace in downtown Warsaw to lay wreaths and express their grief. A national period of mourning was declared and Polish flags were lowered to half-staff.

Condolences poured in from around the world. Including from both Putin and Dmitry Medvedev, the Russian president, who promised a thorough investigation into the causes of the crash.

“Today’s loss is devastating to Poland, to the United States, and to the world,” said a statement from U.S. President Barack Obama. “Today, there are heavy hearts across America. The United States cherishes its deep and abiding bonds with the people of Poland."

The Smolensk airport is mainly a military airfield located not far from the city's center. It lacks some of the more modern navigational aids, and the controller recommended that the Polish government plane divert to Minsk or Moscow because of the difficult conditions. The pilot of the Russian built Tupolev Tu-154 airliner had tried and failed to land three times before clipping some trees and crashing in flames.

Kaczynski was immediately replaced by Bronislaw Komorowski, the speaker of parliament, who takes over the president's duties until new elections are called, which should happen within 60 days.

The loss is unlikely to have a significant impact on the day-to-day functioning of the country.

Bank chief Skrzypek was immediately replaced by his deputy, Piotr Wiesiolek, and the dead military commanders were replaced by their subordinates.

Under the Polish constitution, the president has a more ceremonial function than the prime minister, who is in charge of the government and actually runs the country. Kaczynski had engaged in a long series of disputes over his powers with Tusk, and had usually come off the worst against the popular government leader, leaving the presidency weaker than when he took office in 2005.

Kaczynski had been a controversial president, seen to be in thrall to his twin brother Jaroslaw and to the right-wing Law and Justice party that the two had created in 2001. His support in opinion polls had slipped to about 20 percent, and analysts had predicted that he would lose against Komorowski, the candidate of the ruling Civic Platform party, in elections originally scheduled for this fall.

It is unclear who will be the standard-bearer for Law and Justice in the presidential elections. The likeliest candidates are thought to be Jaroslaw Kaczynski and Zbigniew Ziobro, a popular former justice minister who is currently a member of the European Parliament.

The crash decimated the party's top leadership, which will make it difficult to organize before the snap presidential poll.

Kaczynski was a long-time activist in the anti-communist underground, and had played a role in the formation of the Solidarity trade union in 1980. He was a key negotiator in the transition to democratic rule in 1989, although he later fell out with Lech Walesa, the Nobel Peace Prize laureate and Poland's president from 1990-1995.

Kaczynski was elected president in 2005, and concentrated on cultivating the memory of the losses Poland suffered in World War II, as well as warning against what he saw as dangers to Polish sovereignty from both Russia and Germany. He was a firm ally of the United States, and saw the U.S. as the ultimate guarantor of Poland's security.