Of course it's not possible to determine the source with absolute certainty, but most of the violations had been recorded east of the demarcation line, for instance in this report:

https://www.osce.org/files/2022-02-20-21%20Daily%20Report_EN...

The UN has reported that 81.4% of civilian casualties occurred in territory controlled by the Donbas republics:

https://ukraine.un.org/sites/default/files/2022-02/Conflict-...

Is the reasonable conclusion that these deaths resulted from training and outgoing explosions?