* Being sold in price band of 317.90-328.30 rupees/share
* Citigroup advising Cairn Energy on share sale
Sept 24 (Reuters) - Cairn Energy is selling an 8 percent stake in Cairn India for up to $940 million, a source with direct knowledge of the matter said, in a second such deal in three months to pare holding in its former Indian unit.
Cairn Energy last year sold a controlling stake in Cairn India to London-listed miner Vedanta Resources in an $8.7 billion deal. The British oil firm owned nearly 22 percent of the Indian company as of March 31.
In June, Cairn Energy sold 3.5 percent of Cairn India to raise about $360 million.
Cairn Energy held 18.3 percent of Cairn India as of end-June, stock exchange data showed. After its latest share offering, its stake will fall to about 10 percent.
Cairn Energy on Monday launched an offering of nearly 153 million shares of Cairn India for between 317.90 rupees and 328.30 rupees per share, said the source, who asked not to be identified as he was not authorised to speak to the media.
The range represents a discount of 5-8.7 percent discount from Cairn India's closing price of 345.55 rupees.
Citigroup is the sole bookrunner for the transaction, the source said.