Escalating clashes between pro-Kremlin separatists and Ukrainian forces today killed 15 civilians and forced the new Western-backed leader to cancel a pivotal meeting with Russian President Vladimir Putin at the World Cup in Brazil.
An explosive security crisis just outside the eastern border of the European Union that has claimed more than 550 lives and inflamed East-West relations threatened to spiral into an all-out civil war over the weekend.
Militias that the West and Kiev allege are being armed by the Kremlin used a Grad multiple-rocket system late Friday to mow down 19 Ukrainian soldiers and wound nearly 100 near the Russian border.
Ukrainian President Petro Poroshenko said in a statement issued after phone talks with EU Council President Herman van Rompuy that he wanted the West to condemn "attacks by Russian soldiers of positions held by Ukrainian servicemen".
Poroshenko's statement provided no details of the alleged attack, nor did he indicate whether he was referring to the Grad incident.
Further attacks have since killed 18 more troops and 23 civilians -- 15 of them in what Kiev said were missile and other overnight rebel strikes staged across the eastern rustbelt -- in violence that appeared to shatter any hope of a truce.
Kiev-backed authorities said nine people were killed and at least eight wounded in a suburb of the almost million-strong rebel stronghold of Donetsk.
Municipal workers in neighbouring Lugansk said six people had also died and seven were injured in various incidents in the other separatist bastion of 425,000.
Separatist commander Igor Strelkov said Ukrainian forces responded by sending dozens of tanks to the outskirts of Lugansk in preparation for a possible invasion.
But a spokesman for Ukraine's eastern military campaign said footage aired on Russian state TV of two tanks moving through the Russian border city "was designed to sow panic" and denied that they belonged to government troops.
The civilian toll is one of the highest recorded over a two-day span in a three-month conflict that has threatened the very survival of the strategic ex-Soviet state.
And the military losses have profoundly dampened emerging hopes in Kiev that its recent string of battlefield successes had finally convinced the rebels to sue for peace.
Poroshenko has vowed to kill "hundreds" of gunmen for every lost soldier and ordered an airtight military blockade of Lugansk and Donetsk -- both self-proclaimed capitals of their own "People's Republics".
