MUMBAI, Nov 21 (Reuters) - Royal Dutch Shell is in talks to buy 10 percent of India's Essar Oil as part of a deal where it would sell three European refineries to the Indian firm, the Economic Times reported on Saturday, citing people with knowledge of the plans.

At current market prices, the stake would be worth $364 million (S$505million), the financial daily said. Besides the stake sale, Essar is also looking at raising $1.5 billion in debt as working capital for the three refineries, it said.

"We are in exclusive discussions with Shell. It is not our policy to comment on our negotiations and timelines," an Essar group spokesman told Reuters.

Shell put the plants at Stanlow in northwest England and at Heide and Hamburg in Germany on the market earlier his year and media reports have valued them at between 1 billion-1.5 billion pounds.

Tight margins and falling fuel demand have prompted many big oil companies to offload European refineries and Shell's chief executive Peter Voser said last month it was a challenging time to sell refineries.

Essar, which runs a 280,000 barrels-per-day refinery in western India and owns a 50 percent stake in a Kenyan refinery, is pursuing the deal as part of plans to have a refining capacity of 1 million barrels a day.