Net loss of Rs 10,948.22 crore in January-March compared with a net loss of Rs 240.82 crore in the same period a year ago, the company said in a statement.
"Due to decline in crude oil prices in the international market, the Group has recorded an impairment on the carrying value of goodwill and some of its non-producing oiland gas assets aggregating to Rs 11,389.63 crore and Rs 284.17 crore respectively," it said.
"All the company's projects including Bhagyam and Aishwariya enhanced oil recovery (EOR), Aishwariya Barmer Hill as well as the Raageshwari deep gas project remain viable at the price assumptions taken for impairment," it said.
Production dipped 8 per cent to 206,170 barrels of oil and oil equivalent gas in the fourth quarter of 2015-16. Its mainstay Rajasthan field produced 5 per cent less oil at 164,826 barrels per day.
The company realised an average of USD 27.8 per barrel for oil it produced in January-March, down 43 per cent from USD 48.6 per barrel a year ago. Gas price realisation was however up 19 per cent at USD 7.4 per million standard cubic feet.
For the full 2015-16 fiscal, the company posted a net loss of Rs 9,432 crore as compared to Rs 4,480 crore profit in the previous year.
The loss did not prevent the company board from declaring a Rs 3 per share dividend by dipping into cash reserves of Rs 19,521 crore.
The company has successfully executed one of the world's largest EOR project at Mangala oilfield in Rajasthan block.
"The company continues with its pre-development activities to be future ready to tap the resource base," he said.
Originally, the deal was to close by March 2016 but a
lingering retrospective tax issue and winning over half of the minority shareholders have proved to be a stumbling block.
"The Boards of Vedanta Ltd and Cairn India have today approved revised and final terms for the transaction, taking into account prevailing market conditions and having regard to underlying commercial factors," the two firms said in a joint statement.
Shareholder meetings of Vedanta Ltd and Cairn India will be convened on September 8 and September 12, respectively to get a minority vote on the merger.
Cairn India minority shareholders will own 20.2 per cent and Vedanta Ltd minority shareholders will own a 29.7 per cent stake in the enlarged entity.
After consistently maintaining that the offer of 1:1 share plus one preference share was a fair offer, the Vedanta Group said the sweetened deal "offers significant benefits for Cairn India shareholders by de-risking earnings and stable cash flows supporting investment and dividends through the cycle, driving long-term value".
Anil Agarwal, Chairman of Vedanta Resources plc, said: "The simplified corporate structure will better align interests between all shareholders for the creation of long term sustainable value."
Sudhir Mathur, CFO and Acting CEO of Cairn India, said: "Cairn India shareholders will benefit from exposure to a diversified portfolio of world-class, low cost, long-life assets with significant growth."
"We are confident that the financial strength and diversified portfolio of tier-I assets will provide de-risked earnings and stable cash flows, driving long-term value. Cairn India shareholders will benefit from the revised terms announced today, while retaining the upside from Cairn's strong oil & gas assets," Mathur said.
Stating that companies with diversified resources have delivered superior returns for shareholders historically, he said, "The transaction consolidates our portfolio of attractive tier-I assets and simplifies the group structure, better positioning the group to deliver superior value to all shareholders over the longer term.