The transaction will lead to an open offer for minority holders.
The move comes days after the Indian Navy also warned of a possible terror attack from the sea side.
In a boost to Essar group, the Supreme Court on Monday allowed it to go ahead with its Rs 10,000 crore (Rs 100 billion) oil refinery project at Jamnagar in Gujarat.
Essar group plans to invest an additional Rs 10,000 crore (Rs 100 billion) in Gujarat, starting next financial year, in a bid to make the state the 'petrol capital' of India.
The government has asked Essar Oil to provide within 45 days documentary evidence of deletion of all charges on Ratna R-Series oil fields that were created for raising funds for its Vadinar refinery project.
Financials were the top losers after sharp gains in the previous session along with ITC
The Vedanta group on Wednesday confirmed putting in a preliminary expression of interest (EoI) for buying the government's stake in Bharat Petroleum Corp Ltd (BPCL).
The bench also rejected the submission of senior advocate Mukul Rohatgi, appearing for Essar Oil Ltd, that the hearing be adjourned for four weeks.
ONGC was the top performer while private banking major ICICI Bank extended gains
While the Saudi drone strike has put the focus back on anti-drone measures, caution also stems from the fact that India has a number of large oil refining assets close to India-Pakistan border.
Last June, the group had delisted Essar Energy from the London Stock Exchange as well.
India, the world's fourth-biggest oil consumer, recently offered Saudi Aramco a stake in refineries and petrochemical projects.
ICICI Bank extended yesterday gains, rising 10% in two trading sessions
A preliminary deal for sale of 49 per cent in Essar Oil to Rosneft was signed between the companies in July 2015.
Prime Minister Modi appreciated the vision of Putin for the welfare for Russia's Far East, saying the Russian President has opened up investment opportunities for India in the region.
The surge in deal value is largely due to the $12.9 bn Essar-Rosneft deal
Moscow-based OAO Rosneft Chairman Igor Ivanovich Sechin said the agreement was to ship by sea as much as 10 million tons of oil per year to Essar Group.
'Indian diplomacy in West Asia under the present government has been a success story -- and with Saudi Arabia in particular,' says Ambassador M K Bhadrakumar.
As fuel prices surged in September, the government's decision to ask companies to cut price by Rs1 each on a litre of petrol and diesel came as a dampner for private players.
The Essar Oil, Rosneft deal also helped Arpwood Capital, boutique investment bank, co-founded by Rajeev Gupta and Raj Kataria, to grab the second spot in the mergers and acquisitions league table.
The Rs 3-trillion West Coast or Nanar refinery has all the potential to become India's flagship petrochemicals project, with the planet's largest oil producer Saudi Aramco as its biggest shareholder. Yet the locals don't see the plant as a harbinger of better times.
At $12-bn valuation, this will be India's largest FDI; deal to be announced on Saturday, says Dev Chatterjee.
An estimated 30,000 people along coastal areas will be moved to safer places in Kutch district of Gujarat from Wednesday as the very severe cyclonic storm Nilofar hurtles towards the state and slams it by November 1 afternoon.
Analysts say the Essar Group has been following a policy of delisting just when its businesses begin to record substantial upside, denying shareholders their share of decent returns.
A vilification campaign against Rosneft has begun in right earnest, says M K Bhadrakumar.
'One investor told us one leader in Gujarat had sent him to Konkan to buy land.' 'How did these people come to know about this project in advance when locals didn't know?' 'It means those who are running the country are somewhere interested in selling the country's resources to private businessmen.'
The Sensex had bounced back with gains of 94 points or 0.3%