After months of hesitation, the EU on Saturday agreed to impose economic sanctions against Russia, hoping this "strong warning" would make it change course in Ukraine as fighting intensified around cities held by pro-Russian rebels.
President Vladimir Putin said on Friday Russia's armed forces, backed by its nuclear arsenal, were ready to meet any aggression, declaring at a pro-Kremlin youth camp that foreign states should understand: "It's best not to mess with us."
Blaming Russia for the escalating violence in eastern Ukraine, US President Barack Obama has said that Moscow was deliberately and repeatedly violating the sovereignty and territorial integrity of Ukraine.
East Ukrainian pro-Russian separatist leader Alexander Zakharchenko said serving Russian soldiers, on leave from their posts, are fighting Ukrainian troops alongside the rebels, Russian state television reported.
Reports of funerals of Russian paratroopers need to be checked, President Vladimir Putin`s spokesman said late Wednesday as media speculation mounted over whether the men were killed in action in Ukraine.
Talks between Russian President Vladimir Putin and his Ukrainian counterpart Petro Poroshenko on Wednesday apparently failed to make a major breakthrough towards ending brutal fighting in east Ukraine.
Following Russia`s stand off over Ukraine, Western nations imposed sanctions on Moscow including on its financial and energy sectors, and put dozens of Russians close to President Vladimir Putin on a sanctions list.
Ukraine`s crisis entered dangerous new territory on Saturday with Kiev claiming its forces destroyed a Russian military convoy, while the US warned Moscow over its "provocative" efforts at destabilisation.
The United States has sought clarification from Russia on its "humanitarian convoy" in Ukraine and stated that the escalation in Russian activity designed to destabilise the war-torn nation is dangerous and provocative.