A Ukraininan military plane was shot down by Pro-Russian separatists, killing all 49 crew and troops aboard.
Ukraine's president Petro Poroshenko has vowed to retaliate, saying that "all those involved in cynical acts of terrorism of this magnitude must be punished."
Despite denials from Moscow, the United States believes that the separatists are being armed by Russia. State Department spokesperson Marie Harf said in a statement on Friday:
"We assess that separatists in eastern Ukraine have acquired heavy weapons and military equipment from Russia, including Russian tanks and multiple rocket launchers."
Read more on the Independent.