Cluster of intense bluish white flashing lights, no 'solid' object visible.

Driving in busy town centre at night (could not hear any aircraft noise). Object was of the size of a regular aircraft and at an altitude of only a few hundred feet, but: I could not make out any outline of object; this 'object' was either one craft, or a cluster of three or more extremely bright white 'strobe' lights. What was unusual was that there were no coloured (ie. green/red) lights you'd associate with all light/small aircraft. This craft followed an 'arc' of approx 90 degrees, covering approx 1 mile. The lights disappeared suddenly, strange considering their intensity. The was no low cloud cover, therefore i do not think it was lights being project on/through a cloud base.