One Ukrainian serviceman was killed and three more were injured in the Ukrainian army operation area in the country's east over the past 24 hours. National Security and Defence Council Secretary Oleksandr Turchynov reported this on Friday. "There have been 22 ceasefire violations in the past day," Turchynov said. Russia-backed separatists have been using mortars, large-calibre machine guns, army operation press service reports.