The Obama administration released photographic evidence Sunday it says shows Russian forces fired rockets across the border into eastern Ukraine and that Moscow-backed separatists used heavy weaponry sourced from Russia inside Ukraine.

The evidence bolsters the administration's assertions Thursday that the conflict has taken an ominous turn with direct Russian military involvement. Its release comes as administration officials say they expect European leaders to adopt stringent new economic sanctions against Moscow, based partly on the evidence showing that Russian support for separatists has only increased since Malaysia Airlines Flight 17 was shot down earlier this month.

The U.S. says one of the images provided by the Director of National Intelligence, an aerial shot taken over the weekend and depicting magnified impact craters and blast marks, shows Russians fired "multiple rocket launchers into Ukraine."

Two other images offer evidence that Russia fired artillery into Ukraine last Wednesday, and a fourth depicts multiple rocket launcher strikes within Ukraine last Monday, according to the DNI's office.

The images from last Wednesday show Russian "self-propelled artillery only found in Russian military units," along with the pattern of crater impacts near the Ukrainian military unit, indicating that the strikes originated in Russia.

The fourth image, from July 21, shows the distances between rocket launch sites, indicated by blast marks, and the impact craters where the rockets landed as evidence that Ukrainian military units were the target of fire from multiple rocket launchers, the memo said.

The Obama administration charged on Thursday that Russian forces have fired artillery into Ukraine in an attempt to disrupt Ukrainian military positions. The Pentagon said Friday that Moscow would "imminently" send heavier and more sophisticated rocket systems to the rebels, who have struggled in recent weeks to counter advances by the Ukrainian military.

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