Ukraine's envoy to European security body the OSCE said regular Russian forces had seized the south-eastern city of Novoazovsk, but his Russian counterpart said no Russian forces were crossing the border.
Ihor Prokopchuk, Ukraine's representative to the Organisation for Security and Cooperation in Europe, told reporters that "what we registered is a direct invasion of the Russian military into the eastern regions of Ukraine". He said Ukraine viewed it as an "act of aggression".
Russian Ambassador Andrey Kelin separately told reporters during an extraordinary meeting of the OSCE: "No Russian forces are crossing in any point the border of Ukraine."
A Reuters reporter today saw a column of armoured vehicles and soldiers near a Russian village about two miles from the border with Ukraine.
The reporter said the column was driving away from the border and consisted of two armoured personnel carriers, six military trucks and one military excavator.
Were the Russians -as Barack Obama claims - weighed down by sanctions, or where the Ukrainians looking to cut their losses?
The new president of the European Council could be "very important" for David Cameron.