Kiev - Ukraine said on Tuesday seven of its soldiers had been killed and 14 wounded in "very heated" fighting that marked the bloodiest clashes with pro-Russian separatists in two months.The announcement - the highest daily death toll since Ukraine reported seven of its soldiers dying on May 24 - follows a flurry of talks between world leaders and Moscow on halting the 26-month war."In the past 24 hours, as a result of military operations, seven Ukrainian servicemen died and 14 were injured," military spokesperson Andriy Lysenko told reporters.Lysenko told AFP the fighting had "become very, very heated" in the past few days."Things have escalated for the simple reason that this is what (the rebels) want," Lysenko said. "They do not want to live in peace."The former Soviet republic has been riven by clashes that have claimed nearly 9 500 lives and shattered Moscow's relations with the West.The resulting chill in relations has complicated the West's work with Moscow in trying to bring an end to the Syrian war - a conflict that has seen Russia continue to back the ruling regime and bombard areas controlled by US-backed rebel groups.Ukraine vows swift revengeThe bloodshed drew a vow of immediate revenge from the Ukrainian armed forces chief of staff."Our soul cries for each of our soldiers who lost their lives for Ukraine," Viktor Muzhenko wrote on Facebook. "We will deliver an appropriate response!"The latest violence follows a series of negotiations between EU leaders and Putin about ways to resolve one of Europe's bloodiest conflicts since the 1990s Balkans wars.US Secretary of State John Kerry also raised the issue during a visit to Moscow last week.But neither Kiev nor the insurgents have followed the steps agreed upon in a February 2015 truce deal negotiated with the help of Germany and France.Monitors from the Organization for Security and Co-operation in Europe (OSCE) report that neither side has withdrawn its heaviest weapons from the front line - one of the first points of the pact.The heaviest clashes have come along the 30-kilometre-wide buffer zone the sides agreed to set up during last year's peace negotiations in the Belarussian capital Minsk.The self-proclaimed "people's republics" of Donetsk and Lugansk now control swathes of the Ukrainian industrial heartland and are hoping to stage their own elections that would effectively split them away from Kiev.Ukraine counters that the polls must be conducted under its own rules and result in the rebel-run regions enjoying only partial autonomy for a set number of years.The rebels said on Tuesday that Donetsk separatist leader Aleksander Zakharchenko signed a petition addressed to the UN Security Council demanding that it put more pressure on Kiev to end the bloodshed in the EU's backyard.