The Pentagon and Ukraine on Friday accused Russia of shelling eastern Ukraine and readying more powerful weaponry to send to separatist rebel forces, marking what the Pentgon characterized as an “escalation” of the conflict.

The attacks have been going on for the last several days, Pentagon spokesman Army Col. Steve Warren said. “This is a military escalation, there’s no question about it,” he said. The transfer of more arms could happen “at any moment,” he added.

Evidence of the purported new arms flow is unclear.

Adding fuel to escalating tensions, White House Press Secretary Josh Earnest said Friday that “we have concluded that Vladimir Putin and the Russians are culpable” for the downing of the Malaysia Airlines flight that killed nearly 300 people.

Earnest also cited a comment from vice-chair of the Senate Intel Committee, Sen. Saxby Chambliss (R-Ga.), that “whether it was the Russians themselves that pulled the trigger or Russian separatists trained by Russians, it’s all the same, and it all goes back ultimately to Vladimir Putin.”

Earnest added that this purported evidence “paints a pretty clear picture about what exactly happened and who exactly is responsible.”