"Over the past day there was one of the most intense bombardments of Ukrainian territory since the signing of the Minsk agreement," Ukraine's Security Council said in a statement, referring to the February peace deal.
"Eight Ukrainian soldiers were killed and 16 were wounded," the statement said.
The figure is the highest one-day toll in some five weeks as bombardments around key strategic hotspots continue to rock the truce agreement.
The Security Council said rebel fighters -- that Kiev insists are directed by Russia -- bombarded Ukrainian positions with 152mm cannons but did not specify where the shelling took place.
"The latest events are proof of yet another attempt by Russia and its puppet to wreck the Minsk agreement and restart active military hostilities," the statement said.
The United Nations estimates that more than 6,500 people, most of them civilians, have been killed in the conflict, which began in April 2014, AFP reported.