NATO has called Russia's actions in Ukraine the gravest threat to Europe since the Cold War.
NATO's secretary-general Anders Fogh Rasmussen said Russia's intervention in Ukraine posed the most serious threat to Europe's security since the end of the Cold War.
He also warned Moscow it would face international isolation, news.com.au reports.
According to the report, he said that there had been crises in the Balkans in the 1990s and in Georgia in 2008, but this is the gravest threat to European security.
He demanded Moscow to halt all military activities against Ukraine and seek a peaceful dialogue with Ukraine's government, the report added.