As parliament debated giving Russian-speaking regions in eastern Ukraine more autonomy, right-wing nationalists attacked.
Forces have reached the border of the town of Horlivka and amassed there in the area north of Donetsk.
A HRW report confirmed at least 16 civilians were killed in a series of attacks launched from Ukrainian held territory.
Prime Minister Arseniy Yatsenyuk announced his resignation on Thursday, while explosions echoed through the eastern city of Luhansk.
It's hard to pick a new president when parts of your country are consumed by violence and you've got Russia looming over the border.
Things in Ukraine have been heating up again — with parliament brawls, violent clashes, and official buildings seized by separatists.
In the aftermath of the violent clashes in Donetsk, residents brace themselves for the results of the referendum.