Tried with a different HDMI cable, same issue.
Update: Recently our next flat owners installed Tata Sky HD. I went to their home just now to check this issue. They don't have subscription to all the HD channels. However, they do have Star Maa HD, Star Maa Movies HD and Star Sports 2 HD. The flickering issue is NOT there on their TV. It's a Reconnect brand TV. So, yes it seems to be an issue at my end and not TS. Tomorrow, we should know more once the technician visits.