"Five of our soldiers died and three more were wounded as a result of a landmine explosion" some 45 kilometers (28 miles) from the pro-Russian rebel hub Lugansk, military spokesman Oleksandr Motuzyanyk told reporters.
Seven more soldiers were injured over the past 24 hours in other hotspots in eastern Ukraine, where more than 6,500 people have been killed over the last 15 months.
Motuzyanyk added that the situation in the war zone "remains difficult" and accused the separatists of using artillery prohibited by the Minsk truce deal signed in February.
Daily exchanges of fire have continued to add to the death toll however.
In its latest report published yesterday, the mission of the OSCE said that the situation remained "volatile" at and around Donetsk airport captured by rebels in January after fierce fighting.