A quick googling and literally that report I would say 100% fabrication.There so far aren't any eyewitness reports of a missile incoming, despite there being crowded beaches nearby. I suspect if it's a Ukrainian strike, it's probably something like the quadcopter attack on the VMF HQ in Sevastopol'. It could also be a Ukrainian infiltrator team. Finally never underestimate regular incompetence. This could very well have been a case of dramatic incompetence. Reportedly they're up to 1 killed 13 wounded civilians. Allegedly no military casualties, though I find this doubtful.
EDIT: I'm hearing references in various news articles to a leaked report from Ukrainian Armed Forces commander Zaluzhniy, where Ukraine apparently lost ~191 000 in KIA and WIA, is sufferring from mass desertion, and Ukrainian hospitals are no longer up to the task of handling the heavily wounded. I'm having a hard time locating the report itself, and it's entirely plausible that this leak is a Russian propaganda effort. On the other hand it's not implausible and explains why a 700 000 strong Ukrainian force can't seem to push back ~250 000 Russian troops and associated rebel forces. It also tracks well with the massive discrepancy in firepower, and the rather desperate looking recruiting efforts we're seeing in Ukraine.
So far I'd treat it as possible but completely unconfirmed. I'm going to try and find the original. I suspect it will also be some time before we see corroboration in either direction, unless it gets discredited as a fake.
Ukrainian losses are 191,000 people – even Prof. Vitanov spreads highly dubious data
This site went and looked into it and the source of it was was a Telegram channel "NachStabu " that didnt actually post any pictures of the report but "wrote down" what was allegedly in the report. If you have gotten your hands onto a document with such info your going to be posting pictures of it.
To beleive that would be to believe me when I say that I have got my hands onto internal reports from Alexander Bortnikov the Putin has a midget clown fetish.... I have the documents just not posting pictures just because.....
As it is common sense would dictate if it was so bad we would have heard from other sources on the ground ie: doctors and nurses begging for extra medical help, Ukraine begging EU nations to aid in helping their wounded, and potentially mass graves... Which we havent seen nearly enough of that to indicate casualties of that level IMO.