Poland paid an emotional tribute yesterday to President Lech Kaczynski, his wife Maria and 94 other mostly senior political and military officials killed in a plane crash a week ago in Russia.

Up to 100,000 mourners, many clutching red-and-white national flags threaded with black ribbons, packed into the vast Pilsudski Square in central Warsaw to commemorate the victims of the country's most devastating accident since World War II.

"They all had their dreams and hopes for the future of their homeland. This is a serious test for us to understand those hopes well and take them into the future," Prime Minister Donald Tusk, who had been a political rival of Kaczynski's, told the crowd. "This is the most we can do for them. We are here to remember them. Poland is here to remember them. We will not forget," Tusk said.

Behind him on the podium a tall, white cross rose up between two large black panels bearing the portraits of all the dead, whose names an actor read out one by one.

Kaczynski's twin brother Jaroslaw, a former prime minister who now heads Poland's main opposition party, sat at the front of the mourners with other family members, including the president's daughter Marta(29). Kaczynski had two grandchildren.

Yesterday's commemoration, which included a three-gun salute and a requiem mass, came a day before the planned burial of Kaczynski and his wife in the crypt of Wawel cathedral in Krakow.

World leaders including US president Barack Obama were scheduled to attend the Wawel funeral. But a huge volcanic ash cloud drifting across Europe from Iceland closed Polish airports and it was unclear how many would manage to come. Poland's meteorology institute said the cloud covered all of Poland's territory yesterday but would partly disperse by early today.

Kaczynski and his entourage had been heading last Saturday to Katyn forest near Smolensk in western Russia to commemorate the 70th anniversary of the massacre of 22,000 Polish officers and intellectuals by the Soviet secret police.

The crash has stunned Poland. Tens of thousands lined the streets of Warsaw for the return of the coffins from Russia and the area in front of Kaczynski's palace in Warsaw's Old Town has been transformed into a shrine, bedecked with candles, flowers, crucifixes and flags.

Acting president Bronislaw Komorowski said the tragedy had united Poles of all political beliefs and he also thanked Russia's leaders for their close cooperation immediately after the crash and for their gestures of solidarity.

Last Sunday, Moscow allowed for the first time a state channel to air Polish director Andrzej Wajda's film Katyn, chronicling the 1940 massacre. Until 1990, Moscow had denied Soviet responsibility for the murders, blaming Nazi Germany instead.