epa08218200 Valentina, resident of Petrovsky district, parses rubble in her damaged house after it was hit in a shelling, in the pro-Russian rebels controlled city of Donetsk, Ukraine, 14 February 2020. Ukrainian President Volodymyr Zelensky has had a phone conversation with his Russian counterpart Vladimir Putin on 14 February 2020 to discuss the implementation of the agreements reached during the Normandy Four summit in Paris on 09 December 2019, as well as preparations for another meeting of the leaders of Ukraine, Russia, France and Germany as local media report. EPA-EFE/DAVE MUSTAINE 
Kyiv and Moscow blame each other for a recent spate of violence in the region.
"The prime minister was briefed this morning on this issue, the Russian troop buildup. ... We view this as significant and concerning," said the source, who requested anonymity given the sensitivity of the situation.
"The fact we have troops there means we are more than just casual observers."
A force of 200 Canadian military trainers has been based in western Ukraine since September 2015.
Ukraine's top military official said on Tuesday that Russia was building up armed forces near the border. Moscow responded by saying it feared Kyiv's government forces could do something to restart a conflict with pro-Russian separatists.
Canada, long one of Russia's harshest critics, said on Monday it was imposing sanctions against two Russians and four business entities in response to Moscow's "illegal occupation and annexation" of Crimea in 2014. (Reporting by David Ljunggren; Editing by Peter Cooney)