The simplest way in Windows to turn the monitor off is to call SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, (LPARAM)2);. Unfortunately this call causes the monitor to gradually fade out and since I needed the monitor to turn off immediately I had to find an alternative way.
In order to power the monitor off immediately I ended up using low level monitor configuration functions that provide access to Display Data Channel Command Interface (DDC/CI). To familiarize yourself with these functions please read Using the Low-Level Monitor Configuration Functions.
NOTE: Not all monitors support the DDC/CI power manipulation
I have created Monitors class that powers off/on all the connected monitors. Below is the sample usage: