Russian Strikes Take Toll on Civilians as Ukraine Gears Up for Counteroffensive

In Mykolaiv, near the southern front, residents were jolted awake Sunday by explosions at a warehouse, according to the governor, marking three straight weeks in which artillery strikes have hit the region in the early morning hours. The previous day, two people were killed and five injured in a series of strikes across the region, according to the governor, including several that struck residential areas. A school was also destroyed.

The Sumy region, in the north, was shelled 12 times on Saturday, according to local officials.

Also on Saturday, two Russian Kalibr cruise missiles hit the port of Odessa, a key hub for grain exports, just a day after Ukraine and Russia signed a deal to allow for the safe export of grain from Ukraine. The strike appeared to violate the terms of the United Nations-brokered agreement, which stipulated that both countries would refrain from attacking port facilities or civilian ships. Two more missiles, which Russia has been launching from warships and submarines, were shot down by aerial defenses, officials said.

“Now, it is possible to shoot down some of the missiles,” Ukrainian President Volodymyr Zelensky said in a video posted online late Saturday night. “The goal is to shoot down each one. And we will do everything necessary to still get modern and effective air-defense systems.”

Russian officials have repeatedly said they don’t target civilian areas. After the Odessa port attack, the Russian Foreign Ministry said it was a precision strike that destroyed military infrastructure.

Though the strikes in Mykolaiv have less strategic importance, they are taking a toll on the civilian population of this southern city.

Tatyana Chubanov, a parking attendant in the Korabelny district of Mykolaiv, just 10 miles from the front line, was sitting with a friend in the shed where she works around 6 p.m. on Saturday, when they heard a loud noise, she said. The two women ran out of the shed and took cover behind it. A moment later, a shell struck the parking lot. One car was thrown 30 feet and hit a fence. A bus exploded in flames. Pieces of the vehicles flew hundreds of feet and ripped through the windows of a nearby apartment building. A 16-year-old boy was hit in the chest with a shard of glass and taken to the hospital.

“I wish they would all burn in hell,” Ms. Chubanov, who was crying but uninjured, said of the Russian troops. “We lived so well before they came to our land.”

As she spoke, Alexander Kuznetsov crouched on the ground, sucking fuel out of the destroyed bus through a plastic tube. The bus, which he used to ferry local residents to work each day, had been his livelihood, the father of four said. Only a charred ash-gray frame was left.

“I used to take 50 people to work,” he said. “Now, I don’t know how I’ll do it.”

Mykolaiv Gov. Vitaliy Kim said four Kalibr cruise missiles, which are high-precision weapons, hit the area. But the craters left by the strikes were far smaller than is common with missile attacks, and appeared to be caused by less-precise rockets.

Residents of the area said they heard five or six explosions over the course of about 10 minutes. Vitaliy Selivanov, 39, was at his aunt’s house when he heard an explosion somewhere nearby. He said he ran into the garage, then another shell hit, hurtling him into the air. He hit his head on the ceiling, then fell back to the floor. A pile of bricks and debris landed on him, he said.

“I was trapped for about 15 minutes,” he said. Eventually, his brother found him and dug him out. Covered in dust, he was mostly unhurt, but for a few cuts on his head.

Once he emerged, he saw that the shell had destroyed the house, as well as the home next door. Grape trellises stood untouched, but the houses were turned into piles of smoking metal and glass.

Further strikes are likely as Ukrainian forces prepare their counteroffensive in the south, where they have already retaken several villages.

Last week, Ukraine struck a strategic bridge linking Russian-occupied Kherson with other Russian-held areas in southern Ukraine.

Regaining control of the southern region and the city of Kherson, the only Ukrainian regional capital that Moscow captured in five months of fighting, would hand Kyiv access to another major port hub through which to export grain via the Black Sea.

At the same time, Russia has intensified efforts to potentially annex the southern Ukrainian regions of Kherson and Zaporizhzhia by introducing the Russian ruble in the areas it controls there, appointing officials from Russian provinces to oversee local administrations, switching schools to the Russian curriculum and opening offices to issue Russian passports to local residents.

In Mykolaiv, meanwhile, people are preparing for more frequent attacks as the fighting spreads.

Saturday evening’s strike was the second that Anatoliy Derenuga had endured in 48 hours. On Thursday, he was at a friend’s apartment when a rocket struck near the building. As he ran to get away from the breaking windows, he fell down the stairs, scraping his right arm and leg.

On Saturday, Mr. Derenuga was home with his parents when they heard the air-raid sirens and headed to the basement—protected by a new wooden door they had remade just a few days earlier. The windows exploded minutes later when the shell hit next door.

“All the windows are broken—everything,” his mother, Evgeniya Derenuga, said. “We just rebuilt this house last summer.”

—Mauro Orru and Nikita Nikolaienko contributed to this article.