This is not very common in Australian airspace, but more so in the heavily congested or “politically sensitive” areas of Europe, North America and in certain parts of Asia.
Have a listen to this recording and hear how the communications occurred. Depending on the restricted airspace, further actions will need to be called to escort the aircraft in question either out of the airspace or to the nearest landing zone. This will entail further reports and obviously communications and reporting to the affected organisations.
As an ATCO or commercial pilot, have you ever been involved with a restricted airspace incident? If so, what communications were you involved with?