On the edge of embattled twin cities, an uncovered mass grave for civilians grows.

LYSYCHANSK, Ukraine — A mass grave on the edge of this eastern Ukrainian city remains uncovered. Dirt mounds and yellow-petaled weeds surround a pit filled with a dozen or so body bags. They reek of death in the warm summer wind.

The dead are civilians who were killed by shelling in recent months in the cities of Lysychansk and Sievierodonetsk and the nearby town of Rubizhne. They are heaped together because there are no relatives to claim and bury their bodies.

Standing above the grave, Pvt. Sergiy Veklenko, 41, explained why the bodies were still exposed: “All of our machinery that we had in the city’s inventory — excavators and all — was given to the army for digging trenches.”

As the war grinds into its fourth month and Ukrainian and Russian casualties mount well into the thousands of dead, it is clear that the trenches also have become graves for many soldiers.

Private Veklenko, a former police officer who joined the Ukrainian army when the war began, estimates that 300 people are buried in the mass grave. “We’ve been burying people here who died since April,” he said.

The grave is near a row of hills that is now home to Ukrainian artillery positions defending the city. The howitzers fired off and on through much of Thursday morning.

The number of civilians killed in Lysychansk and Sievierodonetsk, two cities separated by the Siversky Donets River, is unknown. As Russia solidifies control in Sievierodonetsk and shifts its focus to neighboring Lysychansk, civilian casualties there are sure to mount, unless Ukrainian forces retreat.

On Thursday, local officials announced that at least four people had been killed in a Russian airstrike in Lysychansk. The attack happened in the morning, but it took several hours for the news to be posted in official Telegram channels, highlighting the difficulty of communicating what is happening in the city.

Lysychansk, an industrial city with a prewar population of 100,000, is largely cut off from the outside world, with no cell service or electricity. Local officials estimate that 40,000 people remain in the city, though there is no way to know the exact number.

Their reasons for remaining include the need to care for older relatives and, in some cases, even an unwillingness to part with pets.

“Each person does not want to give up their house,” said one woman who emerged from her home to receive supplies from a group of police officers and soldiers on Thursday. “And what about cats and dogs? What about elders? So we sit here.”

“You have to have a lot of money to evacuate, to pay for rent,” she went on, giving only her first name, Luda. “And they don’t allow pets in the rented apartments. I have two dogs and two cats, how can I abandon them? This is not an option, to cry after them later.”

Two people in her neighborhood were killed by shelling about a week ago, she said. They were buried in a patch of woods nearby, their graves marked with a cluster of wilting flowers.

In Sievierodonetsk, about 500 civilians have taken shelter in a large chemical plant, while fighting rages in parts of the city where Ukrainian forces still have control. Officials estimate that 10,000 civilians remain there.

Since the destruction of three bridges connecting the two cities, Ukrainian forces in Sievierodonetsk have had no easy escape routes. On Thursday, there were reports that Ukrainian troops who could cross the river were beginning to pull back to defend Lysychansk, which is on higher ground.

For troops and civilians in Lysychansk, one question lingers: What comes next?

One group of Ukrainian soldiers taking shelter in the basement of an apartment complex voiced hope that advanced rocket systems promised by the United States would arrive soon. The rockets’ longer range would allow them to hit Russian artillery positions. But until the weapons arrive, the soldiers said, the Russian artillery will be relentless.

“One hour feels like an entire day,” one soldier said.