What are these strange rays in the sky?

Those are definitely anticrepuscular rays. The Sun was in the antipodes of the point of convergence of those rays in the sky, when you took that image. Here you have a similar observation:

These are formed just like crepuscular rays; clouds in the direction of the Sun project parallel shadows that cross the entire sky over your head into the opposite direction where the Sun was setting. You see them converging instead of being parallel because of the spherical projection of your spherical field of view (you can reinterpret this as the shadows are closer when they go over your head and are farther from you at the horizon so that rays that are parallel seem to converge at some point at infinity).