What is causing these artefacts?

EPL1, 14-42 kit lens.
This is a night shot, composition dictated by what gravestones I could place the camera on.
If you look at the full size you will see a white arteftact dot in the path and there is one in the tree near the middle (I think the white thing to the right may be an actual object). I turned the camera while still on the same gravestone and took a shot in which there were no artefacts.
I thought it might be something to do with the artificial light sources but today I took a shot today in daylight where there were no artifical lights and that too had 3 white artefact dots, not in the same place within the image.
What's going on?

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Yes, I just read:
'A hot pixel is a pixel that reads high on longer exposures, and can produce white, red, orange, green, or yellow green in longer exposures. The longer the exposure (such as in night photography), the more visible the hot pixels. This phenomenon is caused by the sensor heating up during long exposures. When doing long exposures, use the NOISE REDUCT. option in the menu'

so I think they are indeed hot pixels.

However the shot I took today that had these artefacts was not a long exposure and it was one of the first shots I took today after which I took about 10 others, including one with a long exposure and none of those subsequent shots showed any artefacts. I had noise reduction on throughout today.

 

I've mapped.
It makes 3 shutter movement sounds. Hopefully it's zapped the lights.

 

I tried the shot again and the artefacts were not there this time (but I didn't use as long an exposure).
The light in the tree turned out not to be an artefact but in fact a real light. Although my eyes were only about 3 inches higher than the lens the tree was completely obscuring that light from my view. I was standing there wondering why I could see the light through the live view and I'm looking at the same scene and there's nothing there, it was quite deceptive.