Fierce fighting in east Ukraine has killed at least 11 people over the past 24 hours, officials said on Friday.
A new round of violence threatened a resumption of last summer’s all-out conflict between government forces and pro-Russian rebels.
A military spokesperson Andriy Lysenko reported six soldiers were killed and 18 were wounded in the past day, adding that a civilian was left dead in a rebel strike on a checkpoint near Fashchivka in the Lugansk region.
City officials in Donetsk earlier said four civilians died after shelling sparked a fire at a warehouse there.
Fierce fighting broke out on Thursday around Donetsk airport, a wrecked shell repeatedly hit by battles but still of symbolic and strategic importance. After an overnight lull, there were reports of further intense clashes on Friday.
“A new, very intense assault was launched beginning this morning. There are wounded on our side,” Yuri Biryukov, an adviser to Ukraine’s president, wrote on his Facebook page. “The situation is the worst since late September.”
Clashes have also hit other areas in the east as part of an upsurge in violence in recent days in a conflict that has killed more than 4,800 people since first erupting in April 2014.
Rebels had claimed on Thursday to be on the verge of capturing the airport, but Ukraine’s military on Friday refuted their account.
Heavy artillery and shelling around the airport on Thursday forced monitors from the Organisation for Security and Co-operation in Europe (OSCE) to turn back when attempting to approach it.
The OSCE mission warned of civilian casualties since attacks were being launched from within or around residential areas, drawing counter-fire. It said one of its patrols had come under direct fire from an unknown source in the area of the coastal city of Mariupol, but there was no damage or injuries.
The fresh wave of violence has served as a reminder of the worst days of the war last summer.
On Tuesday, a rocket exploded near a commuter bus on its way to Donetsk, killing 13 people in the worst loss of civilian life in the conflict since a September truce that was meant to bring peace.
Both sides have traded blame for the bus tragedy, while President Petro Poroshenko, in a clear reference to Russia, said ultimate responsibility rested with “those whose hand feeds (the rebels) and arms them.”
Russia, under sanctions from the West over its alleged actions in Ukraine, strongly denies sending troops and weapons into the war zone despite witness claims to the contrary.
Poroshenko has been seeking to organise a summit between him and the leaders of Russia, France and Germany, but it was postponed this week. German chancellor Angela Merkel has said there would be no point in holding it while fighting continues.
On Thursday, Kazakh president Nursultan Nazarbayev and Poroshenko agreed that the delayed talks set for the Kazakhstan capital Astana could take place at the end of the month.