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U.S. officials say 1,000 Russian troops have entered Ukraine as Ukrainian military slam Russia for a "full-scale invasion." CNN's Barbara Starr reports.
The battle for eastern Ukraine continues to rage on as government forces push further against pro-Russian separatists. CNN's Nick Paton Walsh reports on the ongoing violence - as Russia masses more troops on the border.
U.S. officials say they have observed Ukrainian forces firing short-range missiles near pro-Russian rebel positions. CNN's Barbara Starr reports.
After accusing Russia of sending more weapons to separatists and violating an arms ban treaty, the United States is slapping Russia with more sanctions. Michelle Kosinski takes a look at the new sanctions President Obama laid out Tuesday.
CNN's Barbara Starr reports on the evidence the U.S. says it has that implicates Russia in the MH17 plane crash.
CNN's Jim Acosta reports on the two crises that president Obama's administration is simultaneously confronting.
CNN's Barbara Starr reports on new intelligence that may help officials uncover what really happened to flight MH-17.
Putin said that Russian troops would be moved from the Ukraine border, but NATO says they have not seen any withdrawal.
Putin makes his first visit to the disputed region of Crimea since Russia annexed it from Ukraine. Jim Sciutto reports.