NATO: Russian tanks in Ukraine 'a serious escalation of the crisis'

THE HAGUE, Netherlands, June 13 (UPI) -- NATO Secretary General Anders Fogh Rasmussen said Friday that the presence of Russian tanks inside Ukraine "would mark a serious escalation of the crisis."

The secretary general expressed concern about reports that pro-Russian separatists in eastern Ukraine were acquiring heavy weapons and tanks from Russia.

According to the Ukrainian government, three Russian tanks crossed the border into Ukraine via a checkpoint in Luhansk controlled by pro-Russian separatists.

The NATO head directed Russia to withdraw its military from the border with Ukraine, put an end to the flow of fighters and weapons across the border, and urge the armed separatists in Ukraine to put down their weapons.