The surge in clashes across the separatist rust belt spelled an ominous start to campaigning for parties that make the ballot for October 26 parliamentary polls once the registration deadline passes on Tuesday night.
Ukrainian President Petro Poroshenko told German Chancellor Angela Merkel -- his closest and most powerful European ally -- on Monday that Russia was ignoring the terms of a September 5 peace pact the sides sealed in the Belarussian capital Minsk.
Poroshenko "stressed that he expected Russia to fulfil its Minsk Protocol obligations: to withdraw forces, ensure the border's closure, and establish a buffer zone," the presidency said in a statement.
The truce was reinforced with a September 20 deal by each side to pull back 15 kilometres (nine miles) from the front line and allow European monitors to report any resumption of bloodshed that has already claimed more 3,500 lives.
But a weekend attempt by a Russian military delegation to convince the rebels to comply -- a war zone visit that represented a rare if indirect admission by Moscow of its sway over the insurgency -- ended in seeming failure.
The Ukrainian military said militias on Monday launched a tank assault on a long-disputed airport outside the rebel stronghold of Donetsk in which a shell hit an armoured vehicle filled with government troops.
At least nine soldiers died in the strike and ensuing firefight.
Local and Ukrainian state officials said four civilians were also killed in mortar and rocket attacks that spread across the self-proclaimed "people's republics" of Donetsk and Luhansk.
Ukrainian military spokesman Vladyslav Seleznyov told Kiev's Channel 5 television on Tuesday that insurgents were again using Grad multiple rocket launcher systems that have been blamed for destroying scores of civilian homes.
- Poroshenko's election test -
The pro-Western leader's highly controversial decision to promise temporary self-rule for territories under rebel control in exchange for their renouncement of independence has dominated political debate in the run-up to the parliamentary polls.
Poroshenko called the snap vote under pressure to sweep out the Kremlin-backed factions that many see as complicit in winter carnage in which police gunned down nearly 100 pro-European protesters in the heart of Kiev.
The deadliest incident in Ukraine's post-Soviet history forced the former president, Viktor Yanukovych, into self-imposed exile in Russia, and his Regions Party suffered mass abdications that spelled the effective end its dominance in politics.
His successor's newly formed Petro Poroshenko Bloc -- headed by the charismatic and hugely popular former boxing champ Vitali Klitschko -- is the early favourite to finish with the largest share of seats in the new, and far more powerful, parliament.
Future lawmakers will nominate prime ministers and have the right to sack top cabinet members without prior consultation with the president.
But the pro-Western leader is unlikely to secure a majority in the 450-seat chamber.
And his chances of forging a coalition that could help him make peace with Russia while securing a military and economic alliance with the West at present look somewhat remote.
The other main parties that polls show should make it into the new chamber represent either nationalist forces, who reject any deal with the insurgents, or new pro-Russian groups that refuse to accept Ukraine's shift toward the West.
The right-wing contingent includes the People's Front group of Prime Minister Arseniy Yatsenyuk and parliament speaker Oleksandr Turchynov -- dubbed by Moscow as Ukraine's "party of war".
Also likely to make it are the Batkivshchyna (Fatherland) party of ex-premier Yulia Tymoshenko -- an opposition icon stained by sticky corruption allegations -- and the Radical Party of the populist Oleg Lyashko.
Both oppose even a hint of compromise with the rebels and suggest that force may be require to return the Black Sea peninsula of Crimea that Russian seized in the wake of the pro-European revolution in March.