Are nukes bugged in my game, or is this just weird design?

I was going about my business as usual, peaceful empire, my two neighbours relatively like me though I am in no alliances, when suddenly my capital gets nuked?

No notice about it, no indication of who it was, no relationship penalty with anyone over it.

I reload the save and from the colours of the plane, it seems to be my northern neighbour. The game was already basically unwinnable for me, so I decide to just throw a nuke their way too for the hell of it. Devastate their capital too, but still, no relationship penalty, nor am I in war with them now. In fact they are still inviting me to an alliance, while moments later, the exact same tile gets nuked again.

So I am just wondering now, this can surely not be intended?