under surveillance

See: guarded
References in classic literature ?
As I passed along the corridors between the banquet hall and the apartments that had been allotted me, I had a sudden feeling that I was under surveillance, and, turning quickly in my tracks, caught a glimpse of a figure which darted into an open doorway the instant I wheeled about.
All these were Government spies, then, and every spy was under surveillance himself--men spoke in whispers in Venice, and no man trusted his neighbor--not always his own brother.
I think they are here," replied Tarzan, "to prevent us from going some place that they do not wish us to go; in other words we are under surveillance, and possibly as long as we don't go where we are not wanted we shall not be bothered.
They grasped at a myriad clues; hundreds of suspects were jailed, and at various times thousands of suspicious persons were under surveillance, but nothing tangible came to light.