Where are the "rebellious citizens" in Assassin's Creed: Revelations?

To recruit more assassins, the game says to find "rebellious citizens" (as opposed to winning back dens). Where can these citizens be found, and what are their markers on the map?

These are citizens under attack by the guards of the city. They appear on the map as black rectangle with a white circle in the middle and four white Ls in the corners, pointing at the middle.

Citizens will be available to recruit only if you have vacant spots in you assassin's roster. If you assign assassin's as local den master or send them to foreign dens, you'll be able to recruit more assassins.

On a side note, you can always open the map and check the map's legend to determine what is the symbol for every object on the map.

Take a note that potential recruits could not appear until some storyline keypoints passed, also in revelations there is a bit different mechanic for recruits - you should complete short side-quest for getting recruit, not just save citizen from guards as in AC:Brotherhood.