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

The grainy photographs, taken between Wednesday and Saturday, are labeled as indicating fire from multiple rocket launchers inside Russia and targets they have struck inside Ukraine.

The release came as Secretary of State John F. Kerry and Russian Foreign Minister Sergei Lavrov agreed in a telephone call Sunday that “despite disagreements fighting must be stopped” and talks initiated between the warring parties in Ukraine, according to a Russian government statement reported in Moscow by the Interfax news agency. The State Department said the five-minute call included discussions of both Ukraine and Gaza.

As the ground war between Russia-backed separatist forces in eastern Ukraine and government troops has escalated this past week, charges and countercharges between Russia and the West have reached fever pitch.

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

Konashenkov denied recent U.S. statements that Russia, after first decreasing the number of troops it has deployed along the Ukrainian border, has now increased them to at least 15,000. Regular international inspections under the international 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 treaty, member governments regularly conduct overflights, after providing advance notice, of neighboring countries. Although such flights were common in the early days of the Ukrainian conflict, it is unclear whether any have been conducted recently. The U.S. photographs, disseminated by the State Department as “evidence of Russia firing into Ukraine,” were declassified by the U.S. Office of the Director of National Intelligence and presumably taken by U.S. surveillance assets flying overhead.

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

The Pentagon and State Department first accused Russian artillery of firing directly into Ukraine on Thursday. The charges were repeated Friday, although no evidence was offered.

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 by the Office of the Director of National Intelligence.

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

A photograph labeled as 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,” it said.

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

In a statement following President Obama’s call to Netherlands Prime Minister Mark Rutte on Thursday, the White House said the two “agreed that Russia must not be permitted to destabilize the situation in Ukraine without incurring costs and that, accordingly, the international community will need to enact additional sanctions.”

The administration has said it is considering its own additional measures against Russia, while European officials are scheduled to meet this week in Brussels to discuss activating new sanctions against key Russian economic sectors.

Deputy national security adviser Ben Rhodes said Sunday that the United States and Europe are likely to develop stronger sanctions this week against Russia.

“We still think that the best thing the United States can do is send a message to Russia through very strong sanctions coordinated with the Europeans, and I’d expect in the coming days you will see the Europeans move out on stronger sanctions,” Rhodes said on CNN’s “State of the Union.”

Rhodes also said European leaders were open to sanctions against Russia’s energy, arms and financial sectors during talks with Obama in the past week.

Josh Hicks contributed to this report.