Kiev military spokesman Colonel Andriy Lysenko said two government troops died and six were wounded in shelling across swathes of the eastern separatist Donetsk province over the past day.
Lysenko told reporters that "activity had especially picked up" around the industrial Sea of Azov port of Mariupol that the rebels have been trying to seize to establish an export gateway for the steel and coal mines they now control.
Insurgency commanders said rockets launched from Kiev-held positions around the city of Donetsk had killed a civilian and wounded two others in the rebels' main stronghold.
Separatist negotiator Denis Pushilin called the reported attack "a grave violation of the Minsk agreement" that Russia and Ukraine signed during February negotiations spearheaded by the leaders of Germany and France.
The four countries' foreign ministers will meet in Paris on Tuesday to try to salvage the blueprint for ending one of Europe's bloodiest conflicts of the past generation.
But the talks come with East-West relations seeming to test ever new post-Cold War lows.
EU foreign ministers are set Monday to extend expiring trade and financial restrictions on Russia through the end of January.
Those steps stem from claims -- brushed off by President Vladimir Putin -- that Russia is trying to inflict permanent damage on its ex-Soviet neighbour in retribution for Kiev's sudden shift to the West.
Moscow has responded to Western sanctions by imposing a broad ban on US and EU food imports that has hurt European farmers and helped Russian ones boost their sales.
Russia promised over the weekend to keep the trade war going until the West softens its approach.
"We are gradually replacing the foreign food sold on our store shelves with our own" Russian Agriculture Minister Alexander Tkachev said in Moscow.
"And for us, this is happy news."
- Not 'another blathering session' -
Kiev sounded pessimistic about the odds of diplomats walking out of their Paris meeting with a comprehensive solution for Ukraine.
"Paris must not turn into another blathering session," warned Ukrainian Foreign Minster Pavlo Klimkin.
"Either we achieve concrete results, or we demonstrate clearly that Moscow does not want to fulfil the Minsk agreements," he said.
Ukrainian President Petro Poroshenko will send his personal envoy to Minsk on Tuesday to meet Pushilin and other rebels for their own round of European-mediated talks.
A similar meeting last week ended in deadlock and fears of both sides girding for a hot new summer campaign.
"With progress like this, the chances of a complete political settlement of the conflict are in grave doubt," Pushilin said.
The two predominantly Russian-speaking provinces of Luhansk and Donetsk have been waging a war for independence from Kiev's new pro-Western leadership since March 2014.
The conflict has claimed the lives of around 6,500 people and driven an estimated 1.3 million from their homes.
- Competing vision of truce -
Kiev and the insurgents still fail to agree on such basics as where exactly where the Minsk truce line keeping the sides apart runs.
The separatists also want quick local elections that would cement their semi-autonomous status within a unified Ukraine.
But Kiev insists that no such vote can be taken until Ukraine secures full control of the Russian border and "all foreign armed formations" leave the war zone by year-end.
The insurgents on Friday also threatened to keep fighting until Kiev -- in keeping with the Minsk agreement -- amnesties captured fighters not implicated in grave crimes.
The disputes culminated in a disastrous meeting last month that saw the Russian envoy leave the room early and the chief Organization for Security and Co-operation in Europe mediator submitted her resignation soon afterwards.
The OSCE's Heidi Tagliavini is due to be replaced by the end of the month.