WASHINGTON — Stepping up pressure on Moscow, the U.S. has released satellite images it says show that rockets have been fired from Russia into neighboring eastern Ukraine and that heavy artillery for separatists has crossed the border.

The images, which came from the U.S. Director of National Intelligence and could not be independently verified by The Associated Press, show blast marks where rockets were launched and craters where they landed. Officials said Sunday the images show heavy weapons fired between July 21 and July 26 — after the July 17 downing of Malaysia Airlines Flight 17.

The four-page memo is part of the Obama administration’s push to hold Russia accountable for its activities in neighboring Ukraine, and the release could help to persuade the United States’ European allies to apply harsher sanctions on Russia.

The timing of the memo also could be aimed at dissuading Russia from further military posturing. The Pentagon said just days ago that the movement of Russian heavy-caliber artillery systems across its border into Ukraine was “imminent.”

Moscow has angrily denied allegations of Russia’s involvement in eastern Ukraine. Russia’s foreign ministry over the weekend accused the U.S. of conducting “an unrelenting campaign of slander against Russia, ever more relying on open lies.”

The U.S. images claim to show multiple rocket launchers fired at Ukrainian forces from within Ukraine and from Russian soil. One image shows dozens of craters around a Ukrainian military unit and rockets that can travel more than seven miles.