WARSAW, Poland (AP) — Poland's government on Friday marked the 10th anniversary of the plane crash that killed President Lech Kaczynski and 95 others by demanding that Russia return the wreckage of the plane.

Poland's Foreign Ministry said it had sent a diplomatic note to the Russian Embassy in Warsaw calling on Moscow to “immediately surrender Poland's property.”

“No norm of international law gives grounds for Russia’s retention of Poland’s property,” the ministry said.

Poland has made similar demands in the past, and Russia has replied that it is keeping the wreckage of the Tupolev plane because of an ongoing investigation.

The crash occurred as the Tu-154 air force jet carrying a high-level Polish delegation attempted to land in fog at an airport near Smolensk, Russia. It was Poland's worst tragedy since World War II, killing not only the president and first lady, but many other top government and military officials.

The tragedy strained already difficult relations with neighbor Russia. It has also created a deep sense of grievance that has shaped Polish political life since then. Today the government is directed — mostly from behind the scenes — by the late president's identical twin, Jaroslaw Kaczynski, who is chairman of the ruling conservative Law and Justice party.

Kaczynski paid tribute to his twin and other victims at monuments to the victims in Warsaw, at the exact moment that the plane crashed on April 10, 2010.

Prime Minister Mateusz Morawiecki and more than a dozen ruling party politicians also took part despite restrictions imposed because of the coronavirus pandemic that ban gatherings of more than two people.

Police didn't intervene to break up their gathering and some opposition decried what they said were the double standards. Cezary Tomczyk, a lawmaker with the centrist Civic Platform party, called it “outrageous” that parks and forests have been closed, and high fines handed out to regular citizens, while politicians gathered like that.

“Yesterday a hairdresser got a fine of 10,000 zlotys ($2,400) for opening the business for one client,” Tomczyk said. “What kind of example is this? What kind of hypocrisy?”

The fact that the delegation killed in the plane crash had been traveling to commemorate a World War II massacre of some 22,000 Polish officers by the Soviet Union deepened the sense of national tragedy.

This year, Polish leaders had hoped to travel to Russia to mark the anniversary, but a government spokesman said Russia didn't provide the Polish government with the logistical support needed to organize the visit.