The situation within the area of a military operation that the Ukrainian government forces are conducting in the eastern part of the country remains complicated, and the militants keep on shelling government forces' positions with howitzers, cannons, and mortars, Ukrainian presidential spokesman for military issues Oleksandr Motuzianyk said.

"The tension has grown over the past 24 hours, the enemy has been actively using tube artillery and mortars, especially at the Mariupol front," Motuzianyk said at a news conference in Kyiv on Saturday.

At the Luhansk front, the enemy shelled Ukrainian government forces' positions with large-caliber cannons near Valuiske, Motuzianyk said.

The militants also fired upon Ukrainian defense lines near Novotoshkivske with antitank grenade launchers and mortars, and the situation near Zolote was also not calm, he said.

"The shelling with mortars was started at noon and lasted until late in the evening. At the same time, an enemy sabotage and reconnaissance group attempted to break through the defense line in this area," he said.

The militants had to retreat after the clash, Motuzianyk said. "The enemy has used mortars, 122mm artillery, and Grad Partisan portable rocket launchers near Zolote over the past 24 hours," he said.

The militants have also repeatedly shelled Ukrainian government forces' positions near Popasna with mortars and artillery pieces, Motuzianyk said. The outskirts of Troitske were shelled only at night with 82mm mortars, he said.

At the Donetsk front east of the Svitlodar reservoir, the militants committed a number of provocative acts after midnight, after which they stopped their activities there, he said.

West of the reservoir, several ceasefire violations were recorded near the community of Zaitseve; in particular, Ukrainian government forces' defense lines were shelled with large-caliber machineguns, he said.

"In other suburbs of Horlivka, the situation last night was relatively calm," he said.

The situation near the Donetsk airport remained complicated, Motuzianyk said. "The enemy keeps provoking the Ukrainian military into returning fire, using small arms and mortars. Heavy weapons have not been used in this area over the past 24 hours," he said.

The situation at the Mariupol front also remained complicated, Motuzianyk said. "Mainly heavy artillery has been used. In particular, Ukrainian strongholds not far from Bohdanivka, Prokhorivka, Starohnativka, Lebedynske, and Vynohradne east of Mariupol have been shelled," he said.

Residential quarters of Prokhorivka, the Volnovakha district, have been shelled with howitzers, Motuzianyk said. It was determined that the fire had been directed from an elevated area near Bila Kamyanka controlled by the militants, where the latter were active from midnight until 10:00 a.m., he said.