Thank you for the detailed replies @Srikumar, @Islam Soliman and @Gaurav.
@Srikumar I do not think it is the sound of rubbing, not sure about wheel bearing sound though.
I do not have the front skid plate installed and after every offroad drive the tyre did start slightly touching the front back bumper at certain angles but I got it fixed each time. This noise problem existed before my first ever offroad drive, (which was with you @Srikumar BTW ) so it seems unrelated.
From the driver's seat, the noise does not seem to be coming from left or right, but almost center.
Heeding advice from you guys, I decided to visit my garage today and luckily the noise started when I was about to reach the garage. I called the mechanic out on the road and was able to demonstrate the noise to him while slowly driving past him. Later we put the car on a lift and tried spinning the wheels in 2H and 4H. The mechanic concluded that the noise is not related to the wheel bearings but he pointed to the front differential and said the noise seems to be coming from there. Also he pointed to fluid leaking from the differential. I have taken a picture of the part that he suggested to be faulty:
After leaving the garage, I got the noise again. I tried switching from 2H to 4H and the noise just went off when the car switched to 4H. As I had mentioned before, the noise problem never occurred while off-roading when I was always in 4H.
Googling for "Pajero front differential issues", found me some posts on various off-roading forums that had people complaining about the exact same symptoms as me. The final solution was replacement of either solenoids, actuators or both.
I am going to get a second opinion about the wheel bearings and front diff from Al Habtoor before getting anything fixed. Would also appreciate any further comments from you guys.