Dark discoid object playing amongst the clouds later chased by 2 brilliant white disks.While playing with my grandchildren in our backyard, we saw a disk-shaped black or dark UFO at about 12 miles distance hovering between 6000 to 15000 feet, moving up and down and then sideways - almost fluttering amongst the clouds, acting very much like someone doing semaphore signals.All of the sudden, after abt 12 mins. of this actios, the saucer stabilized itself at a height of abt 12k feet and started moving in a north by northwest heading, at first slowly, then speeding up. Abt 1 minute later, two saucershaped disks - brilliant white in appearance, came from the east-northeast direction and went in pursuit of the other blackship, at the same height and at a leisurely pace and they were visualized until they got lost in the horizon.All along, and during this experience, we could also observe two motorized hang-gliders that were manouvering to and from the ocean close to us - abt 2 kms - but it seems they did not notice the saucer's games because of the height.Our location is 18°21'North lat. and 66°75'West long.