Ukrainian Prime Minister Arseniy Yatsenyuk today accused Russia of wanting to start "a third world war" over his country and called for international help against "Russian aggression".
"The aggressive efforts of the Russian military on Ukraine's soil will lead to a conflict on European soil," he said in a televised cabinet meeting.
"The world hasn't forgotten the Second World War and Russia wants to start a third world war," he said.
"Russia's support for the terrorists in Ukraine constitutes an international crime and we call on the international community to unite against the Russian aggression."
Kiev's Western-backed government believes Moscow is pulling the strings in the separatist rebellion in Ukraine's east.
Russia yesterday announced it was launched new military exercises on the border with Ukraine in response to an "anti-terrorist" operation Kiev is waging against the pro-Kremlin rebels.
An estimated 40,000 Russian troops are massed on the border, according to NATO, which has said they appear to be in a state of readiness to invade.