Rebels and government troops fired on each other’s positions Sunday in a strategically important city in eastern Ukraine, sending residents into bomb shelters, as Washington released images that it said prove Russia is shooting across the border into Ukraine to support separatists.

At least 13 civilians were reported killed in the fighting around Horlivka, an industrial city of almost 300,000 people about 30 miles from the rebel bastion of Donetsk. According to a resident reached by telephone, parts of the city are without water or electricity, grocery stores are empty, and rebels and residents are fleeing.

The Ukrainian military denied targeting civilians and said the pro-Russian rebels were to blame for the damage and casualties. The military accused the rebels of firing into residential neighborhoods.

The battle in Horlivka is part of a major push by the military to isolate and eventually oust the rebel fighters from the self-proclaimed Donetsk People’s Republic. It would be a huge symbolic and strategic victory.

As the fighting raged, Secretary of State John F. Kerry and Russian Foreign Minister Sergei Lavrov talked briefly on the phone. According to a Russian Foreign Ministry statement, they discussed the need for an “immediate” cease-fire in Ukraine. The State Department said that during the short call, Kerry urged Lavrov “to stop the flow of heavy weapons and rocket and artillery fire from Russia into Ukraine, and to begin to contribute to deescalating the conflict. He did not accept Foreign Minister Lavrov’s denial that heavy weapons from Russia were contributing to the conflict.”

Residential areas in the eastern Ukrainian town of Horlivka and a checkpoint at Ukraine’s Krasna Talivka border crossing were destroyed in two separate attacks. Ukraine’s defense council blamed separatists for the attacks as fighting continues in eastern Ukraine. (Divya Jeswani Verma/The Washington Post)

As the ground war in eastern Ukraine between Russian-backed separatist forces and government troops has escalated, the war of words and images between Russia and the West has reached a fever pitch.

The Obama administration on Sunday released grainy surveillance photographs that it said were evidence that Russia has fired artillery rounds from its side of the border on Ukrainian military units.

Maj. Gen. Igor Konashenkov, a Russian Defense Ministry spokesman, charged Sunday that the United States is getting most of its intelligence on the Russian military from social media and suggested that it turn to more “trustworthy” information, the news agency Itar-Tass reported.

Konashenkov denied U.S. statements last week that Russia, after first decreasing the number of its troops deployed along the Ukraine border, has increased their ranks to at least 15,000. Regular international inspections under the Open Skies Treaty, he said, “have not registered any violations or undeclared military activity on the part of Russia in the areas adjacent to the Ukrainian border.”

Under the international treaty, member governments regularly conduct overflights, after providing advance notice, of neighboring countries. Although such flights were common in the early days of the Ukraine conflict, it is unclear whether any have been conducted recently.

Konashenkov said similar inspections of “Ukrainian armed forces’ active combat actions in the areas adjacent to the Russian border” would register a “high concentration of Ukrainian troops, armaments and military equipment that regularly shell Russian settlements and have already killed and injured our citizens there.”

The State Department and the Office of the Director of National Intelligence, both of which distributed the photographs to journalists Sunday, did not indicate the source of the images, which were labeled with the imprint of Digital Globe, a commercial satellite and aerial-imaging company.

The high-altitude images released Sunday “provide evidence that Russian forces have fired across the border at Ukrainian military forces, and that Russia-backed separatists have used heavy artillery, provided by Russia, in attacks on Ukrainian forces from inside Ukraine,” according to labels on the pictures provided by the U.S. government.

The most recent photograph, taken Saturday, shows what are described as “blast marks” from rocket-launcher fire on the Russian side of the border and “impact craters” inside Ukraine.

A photograph labeled as having been taken Wednesday shows a row of vehicles described as “self-propelled artillery only found in Russian military units, on the Russian side of the border, oriented in the direction of a Ukrainian military unit within Ukraine.” On the other side of the border, “the pattern of crater impacts near the Ukrainian military unit indicates strikes from artillery fired from self-propelled or towed artillery, vice multiple rocket launchers,” the label says.

The Obama administration has said that direct Russian participation in Ukraine, along with Moscow’s failure to use its influence on the separatists to allow international inspectors access to the site of the July 17 Malaysian airliner crash inside separatist territory, should lead to increased sanctions against Russia.

A team of forensic experts and investigators that arrived Sunday in Donetsk had planned to head to the crash site, but the visit was called off for safety reasons.

Sunday marked the third day of the Ukrainian army’s assault on rebels in Horlivka. Some residents said shelling began shortly after dawn and continued intermittently throughout the day.

Andriy Lysenko, a Ukrainian military spokesman, said troops are not carrying out air or artillery strikes against civilians. He blamed the attacks on rebels, who he said are trying to frighten residents and discredit the army by posing as government troops.

A video taken Sunday in Horlivka showed large plumes of gray smoke rising from several places in the city.

A resident named Viktor, a 32-year-old engineer who asked that his last name not be published because of the precarious situation, said he watched from his sixth-floor balcony as army troops and rebels exchanged fire. He said he saw rockets launched from a rebel position answered by return fire a few minutes later.

The weapons fire ignited the local energy company’s office, struck a supermarket on the ground floor of an apartment building and destroyed a building housing the kitchen of the local hospital, he said.

Viktor described an eerie emptiness in Horlivka. Traffic, he said, is mostly just a few speeding cars that appear to be driven by rebels. Residents who live in houses are spending nights in their basements, he said, while apartment dwellers have retreated to abandoned Soviet-era bomb shelters that smell of sewage.

“A lot of people have left,” Viktor said. “But my mother is here, and I can’t leave her.”

DeYoung reported from Washington. Karoun Demirjian in St. Petersburg and Alex Ryabchyn in Kiev contributed to this report.