The latest deaths highlight the fragile nature of a February ceasefire aimed at halting the conflict and come shortly before talks next week aimed at salvaging the deal.
Fighting has intensified recently around key hotspots on the frontline in industrial eastern Ukraine, particularly the outskirts of the strategic government-held port city of Mariupol and Donetsk airport.
Two soldiers were killed today and a third was wounded in a battle in Marinka, about 30 kilometres (20 miles) west of the rebel stronghold of Donetsk, a local military spokesman Evgen Silkin told AFP.
He said a 55-year-old civilian and his 14-year-old son were also killed by a makeshift bomb which blew up in Stanitsa Luganska.
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Another soldier was killed in Shirokine, another flashpoint just 10 kilometres away from Mariupol, the last remaining government-held city in the conflict zone.
The Organisation for Security and Cooperation in Europe, which has monitors on the ground in eastern Ukraine, has denounced a surge in violations of the February truce.
The conflict, which erupted in April 2014, has claimed the lives of almost 6,300 people.