These satellite photos show Russia committing an act of overt war against Ukraine

The US State Department has released satellite photos that it says prove that Russia is using its artillery to fire into Ukrainian territory at Ukrainian military forces. Ukraine has been claiming for weeks that Russia was firing artillery across its border — an act of overt war — but the US did not confirm it until Thursday.

If true, this would be a major escalation by Moscow; for Russia to use its military openly to attack Ukrainian forces would be a step beyond its prior strategy of sending in unmarked special forces and backing separatist rebels. While this is still not as significant as Russia’s invasion and annexation of Crimea in March, it is a big step up in Russia’s eastern Ukraine actions.

While Ukraine says the shelling began some time before flight MH17 was shot down over eastern Ukraine, most likely by Russia-backed rebels, this report comes at a time when the world is already moving to punish Russian President Vladimir Putin for his actions. It appears that the US is releasing the photos now to further isolate Putin and galvanize European leaders to join sanctions against him.

Here are a few of the photos, tweeted by US Ambassador to Ukraine Geoffrey Pyatt:

The photos, according to the State Department, were taken after flight MH17 was shot down, indicating that the incident has not chastened Russia’s attacks on Ukraine.

The US, with these announcements, is clearly trying to at least deter Putin from deepening his military involvement in eastern Ukraine. But the fact that Russia continues to escalate there is a sign that something bigger will have to happen for Putin to step back from the region.