Ukraine war briefing: Moscow warns of retaliation after blaming US for deadly Ukrainian attack The GuardianRussia promises retaliation against US for Ukraine strike on Crimea Reuters.comRussia tells US ambassador it will retaliate over Sevastopol missile strike Al Jazeera EnglishRussia summons the American ambassador over a deadly attack that Moscow says used US-made missiles Yahoo! VoicesU.S. Disputes Russia’s Claim About Responsibility For Strike On Crimea Radio Free Europe / Radio Liberty