Thank you everyone for the advice.
It turned out to be (as per the mechanic in Pwd Rawalpindi/isb) a short-circuit in immobilizer system, burned ICs which caused the 12v to die as well.
Mechanic has apparently reprogrammed the immobilizer and replaced the battery.
He charged me Rs 13,000 for immobilizer repair.
I guess I got ripped off.
Feel free to guide/advise me further.
Thanks again