the deal to end a bitter 10-month-long conflict may be in jeopardy.
Both incoming and outgoing artillery could be seen in the vicinity of the coastal city of Mariupol, and there was significant shelling in Donetsk through the morning, CNN teams reported.
The continued conflict comes after Ukraine's President Petro Poroshenko warned Friday that the planned ceasefire between Ukrainian forces and pro-Russian separatists was in "big danger."
Poroshenko said that after the agreement reached Thursday by the leaders of Ukraine, Russia, Germany and France, the offensive against Ukrainian troops by the separatists had intensified.
The separatists may be trying to take control of strategic locations, such as the railroad hub of Debaltseve to the north, before the ceasefire lines are drawn. Pro-Kiev militia have also been pushing forward around government-controlled Mariupol.
As the shells rain down, the toll on eastern Ukraine's residents only grows.
The Ukrainian military operation against the separatists said Friday that 14 civilians had been killed by rebel shelling, six in the village of Shchastya, five in the village of Hornyak and three in Artemivsk, according to the official Ukrinform news agency.
Each side has accused the other of shelling civilian areas in the course of a conflict that has killed more than 5,000 people.
The peace agreement signed in Minsk, Belarus, comes with many questions over how it will be implemented and whether it will stick.