Thanks to Toby Clark for pointing out this artist to me.
The verdict is that the photographs were taken by combining a series of long exposures, so maybe something like 6 exposures of one second each on top of each other. You can work this out by looking at the trainer at the bottom of the first image. Great subject matter – people boiling over a city. I’d like to have a go at this technique over the summer, using video frames, people braising in London.
More images by the Russian photographer can be seen here