ONGC said the loans are of one-year duration. The pact with PNB is for loan of up to Rs 106 billion and with Bank of India for another Rs 44.60 billion.
With Axis Bank it has secured Rs 30 billion credit.
The company is likely to sign-up more loan agreements to pay for acquiring government's 51.11 per cent stake in HPCL for Rs 369.15 billion.
ONGC is to pay the government for the stake within this month.
The acquisition would create India's first integrated oil company. This would be ONGC's biggest acquisition and second buyout this fiscal after its Rs 77.38 billion acquisition of 80 per cent stake in Gujarat State Petroleum Corp's KG basin gas block.
ONGC Chairman and Managing Director Shashi Shanker had on Sunday stated that the company's board has approved raising of the borrowing limit from Rs 250 billion to Rs 350 billion.
This will be the company's first ever debt.
"We will use our (Rs 120-130 billion) cash first and then the liquid assets and debt will be last," he had said. "This order can change, because we won't sell the liquid assets in distress. Also, we have offers for over Rs 500 billion debt at very competitive rates, both foreign currency and local."
ONGC holds 13.77 per cent stake in Indian Oil Corp (IOC), which is worth over Rs 260 billion. It also holds 4.86 per cent stake in GAIL India Ltd, which is worth over Rs 38 billion.
The company had on January 20 announced buying of government's 51.11 per cent stake in India's third largest state-owned oil refiner and marketing company for Rs 473.97 per share in an all-cash deal that is to be closed before the month-end.