Two circles of white 'cloudy' balls (rotating in opposite directions), no sound.

After working, when I cycled home along the long street I was then living in, I noticed a formation of balls, that mooved ahead of me (about a 100 meters) in the same speed as I cycled. It seemed to me that the hight was about 10 meters. The formation floated over the trees at the right site of the street. There was no sound. There was no wind that night. It was about 17 degrees Celcius. The formation was made of completely round balls in two circles. The balls in the inner circle were bigger as the balls in the outer circle. They were 'made of' white smoke or clouds (misty?). When I reached my house and stopped, the formation also stopped mooving and I watched it for quite some time. The inner circle rotated slowly in the opposite direction as the outer circle. I looked around if one of the neighbours was still awake, in order to ask somebody if I was imagining this event, but I saw no lights burning. I had to feed my pats and so I entered the house. In the backgarden I tried to find the formation in the sky, but couldn't find it. When I left my house again, the formation was gone. I felt uncomfortable. I cycled back to the centre of town to meet my husband and friends and told them what I saw. I could not give an explanation and realised that I had seen a UFO. One friend told about lasershows, projecting light on clowds, but I was sure I had not seen something like that. A few months later I saw a show like that and this was something completely different. About a year back I saw a picture on Discovery Channel of a UFO that was seen in (if I remember well) Australia, simular to what I had seen. This is the first time I report my observation.
Date is approximate.  PD