Bellingcat: "artillery attacks on Ukrainian territory and against Ukrainian forces originated from the territory of Russia"

There is clear evidence that heavy Russian artillery, based on the Russian side of the border, has played a crucial role in the fighting in Ukraine:

Ukrainian armed forces positioned near the Russian-Ukrainian border were attacked by artillery fire in the summer of 2014. Between 9 July and 5 September 2014, the Ukrainian Border Service and the National Security and Defense Council reported more than 120 artillery attacks from Russia. Russian officials, however, have denied the existence of any artillery attacks on Ukraine originating from its territory.
The pressure of sustained artillery attacks through early August led Ukrainian armed forces to lose control of hundreds of kilometers of border territory. Google Earth satellite images of eastern Ukraine from July, August, and September 2014 have enabled the Bellingcat investigation team to find evidence of these artillery attacks, determine their origin, and compare them with local sources.
After reviewing and analyzing these satellite images as well as videos from social media, local media reports, and the shifting maps of the ongoing conflict, the Bellingcat investigation team has determined that there is compelling evidence that artillery attacks on Ukrainian territory and against Ukrainian armed forces originated from the territory of Russia.