“We assess that separatists in eastern Ukraine have acquired heavy weapons and military equipment from Russia, including Russian tanks and multiple rocket launchers,” State Department deputy spokeswoman Marie Harf said in a statement.
Harf said video footage posted online showed Russian tanks departing a site in southwest Russia and moving through multiple cities in east Ukraine.
Ukraine’s interior minister, Arseny Avakov, said on Thursday that three Russian tanks crossed into Ukrainian territory and were attacked by Ukrainian forces, France24 reported.
Harf confirmed that a convoy of three T-64 tanks, several MB-21 “or Grad” multiple rocket launchers and other military vehicles had crossed the border in the last three days.
“This is unacceptable,” Harf told the briefing. “A failure by Russia to de-escalate the situation will lead to additional costs.”
The United States and European allies have threatened broader sanctions against Russia unless Moscow stops assisting rebels in eastern Ukraine.
“Russia will claim these tanks were taken from Ukrainian forces, but no Ukrainian tank unit has been operating in that area,” Harf said. “We are confident that these tanks came from Russia.
She said multiple rocket launchers, which were at the same deployment site in southwest Russia, were seen traveling through the Ukrainian city of Luhansk.
Ukraine’s new president, Petro Porochenko, had spoken to Russia’s Vladimir Putin on Thursday about the issue, while US Secretary of State John Kerry raised concerns with his Russian counterpart Sergei Lavrov, Harf said.