Ukraine has accused Russia of bringing three tanks into the east of the country to fight the Ukrainian army.
Interior Minister Arseny Avakov suggested separatist rebels had brought three tanks and other military vehicles across the border.
While he did not directly accuse Russia of sending the tanks, he made clear he held President Vladimir Putin responsible for failing to carry out a promise to tighten controls at the border.
More top news
Pharmaceutical giant Roche is trialling a new type of treatment which could work better than chemotherapy.
Old Labour firebrand Derek Hatton is now locked in a new fight - to rejoin his old party.
After a career which began with carrying Britain's first nuclear bombs, the last flying Vulcan Bomber is being retired.