Ukraine clashes kill 15 civilians, Putin talks nixed

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".

European leaders responded by joining forces with Putin in a bid to convince Poroshenko to put the brakes on violence first sparked by the February ouster of a Kremlin-backed president and fanned by Russia's subsequent seizure of Crimea.

The immediate hopes of a truce rested on a meeting between Putin and Poroshenko - the second since the Ukrainian president's May 25 election — that seemed on the cards on the sidelines of the World Cup final in Rio de Janeiro.

But the Ukrainian presidency said early on Sunday that Poroshenko was forced to cancel his attendance "considering the situation currently happening in Ukraine".

Putin instead met Merkel for talks the Kremlin said ended with a call on the warring sides to issue "a statement as soon as possible concerning a ceasefire, a prisoner swap, and the return of (international) monitors" to eastern Ukraine.

A German government spokesman said Putin and Merkel suggested that Kiev and the separatists launch their discussions "by video conference".

The separatists' use of Grad systems — featured heavily in Russia's devastating assault on the Chechen capital Grozny in the 1990s — has underpinned the most recent charges that the Kremlin is directly involved in the insurgency.

Putin rejects accusations of orchestrating the uprising to retain partial control over eastern Ukraine and punish Kiev for its decision to strike a historic EU alliance instead of a new Kremlin pact.

But Poroshenko argues that no truce with the rebels is possible until his troops manage to seal the Russian border and halt the continuing flow of gunmen and arms.

The frontier became the conflict's new frontline after last weekend's evacuation by the rebels of a host of towns and cities that they had held since early April in the coal mining region of Donetsk.

The militias have since concentrated their forces around the cities of Donetsk and Lugansk and are hoping for new weapons deliveries to revive their campaign.

Fresh tension emerged with claims by Moscow of a Ukrainian shell killing a civilian near a small Russian border town.

The Russian foreign ministry called the episode "another act of aggression" that could have "irreversible consequences" for Ukraine.

The Ukrainian foreign ministry said government forces "had never before, are not now, and never will fire on the territory of a neighbouring state".