In Ukraine, no one is quite sure exactly what that toll is, except that many many people have been killed.

An “endless caravan of death,” said Petro Andryushchenko, an official for the devastated city of Mariupol.

In its latest updates, the Office of United Nations High Commissioner for Human Rights said 4,509 civilians had been killed in the conflict. But it is clear that many thousands more have been killed. Ukraine’s chief of police, Ihor Klymenko, said this past week that prosecutors had opened criminal proceedings “for the deaths of more than 12,000 people who were found, in particular, in mass graves.”

And in Mariupol, the Black Sea city flattened by Russian bombardment, Ukrainian officials in exile have said that examinations of mass graves using satellite imagery, witness testimony and other evidence have led them to believe that at least 22,000 were killed — and possibly thousands more.

The casualty figures exclude the thousands believed killed in territories held by Russian forces. And even where Ukraine has regained control, Mr. Klymenko said, it was premature to calculate the dead in mass graves, as more are found every week.

Indeed, finding and identifying the dead is such a daunting challenge, Ukraine’s chief prosecutor said in a statement on Saturday, that it required global coordination beyond Ukraine’s national efforts. The prosecutor, Iryna Venediktova, said she had met with the International Commission on Missing Persons, based in The Hague, to develop avenues for cooperation.

International and Ukrainian authorities have little access to embattled cities to take accurate counts, and the urban targets, the constant artillery fire and the static nature of the fighting in the contested south and east only adds to the death and horror.

“People are killed indiscriminately or suddenly or without rhyme or reason,” said Richard H. Kohn, a professor emeritus of history and peace, war and defense at the University of North Carolina at Chapel Hill. He said the incessant artillery fire “kills and maims people.”

“It creates enormous psychological stress on populations,” Mr. Kohn said, “as it does on the combatants,” and “it lasts for a very long time.”

The Russians, eager to preserve an aura of competence, underreport their battlefield losses. The Ukrainians, desperate to maintain morale as the shells fall, do the same. Civilian casualties are an unknown variable, multiplied by grisly factors like collapsing buildings and the unreported victims of occupied towns.

Children are not protected from the indiscriminate violence. The United Nations’ agency for the protection of children in emergency situations has estimated that at least three children have died each day since the war started in February. That is only an estimate.

Mariupol — the city that has become symbolic of Ukraine’s resistance, Russia’s unrelenting shelling and the war’s savagery — is still burying corpses.

“In our city, there are a lot of mass graves, a lot of spontaneous graves, and some bodies are still in the street,” Mariupol’s mayor, Vadym Boichenko, said last Monday.

That toll has heightened dread about the losses in the 20 percent of Ukraine now under Russian occupation. Some places, like Sievierodonetsk, have been basically reduced to rubble by advancing Russian forces.

Early in the war, as Russia tried, and failed, to take the capital, Kyiv, its forces added to the death toll with shocking brutality. In Bucha, they shot civilians dead in their cars, homes and gardens, left corpses in the street and even burned them and dumped them in a parking lot. And when the Russian armored columns retreated, they left more dead in their wake.

At least 1,500 civilians were killed in the Kyiv region alone, according to Mr. Klymenko. They included two sisters in Bucha — one a retired teacher and the other disabled.

“Why would you kill a grandma?” asked Serhiy, a neighbor of the sisters.

The Ukrainian army is taking heavy losses. By the government’s own estimates, as many as 200 soldiers are dying every day. In towns and cities across the country, even those far from the front lines, military funerals take place nearly daily for Ukrainian soldiers killed in the Luhansk and Donetsk regions, where the fighting is now heaviest.

The dead are often buried quickly, and in shallow graves.

“I feel numb,” said Antoniy, a morgue worker in Lviv, in western Ukraine. “Even when someone is telling me a joke that I know is funny, I can’t laugh.”

Regardless of when or how the war ends, Professor Kohn said, trauma, loss, displacement and fear all become “part of the culture of a country.”

Many of the Russians ordered by President Vladimir V. Putin to invade Ukraine under the false pretenses of liberating the country from Nazis are not coming home, either. In April, Western countries estimated that Russia had lost about 15,000 soldiers in Ukraine; on Friday, Ukraine put the estimate at 33,000.

The true toll is unknown, and will not be coming from Moscow: Its last announcement, on March 25, said that a total of 1,351 Russian soldiers had died.

In the months after the invasion began, local news websites across Russia compiled “memory pages” that listed the names of hometown soldiers who had died. Then, this month, they deleted them: A court ruled that such lists were state secrets.

“We apologize,” said the site 74.ru in Chelyabinsk in Siberia, “to the mothers and fathers, wives and children, relatives and friends of the servicemen who have died during the special military operation in Ukraine.”