I'm using the default World Sky texture settings for my scene. There's a dark bluish rectangle positioned at the middle of the sky texture when rendered as compared to its appearance in the 3D viewport.
How do I fix the issue?
Turns out the End Clipping of the camera (Max viewing distance) was the one causing the issue. I down-scaled all the objects in my scene and set the clipping distance of my camera from 1500 down to 100 and that fixed the problem.
Do not set your render distance past 200 as it will most likely give you clipping issues.