The investment, Bharti said, will "further strengthen its capital structure and provide further flexibility to the company to deliver on its growth strategy".
As part of the agreement, Bharti will issue 199.8 million new shares at 340 rupees ($6.2) per share, which investor Qatar Foundation Endowment (QFE) will acquire, the Indian firm said in a statement.
This is a 7.5 percent premium to Bharti's closing price of 316 rupees on Thursday.
The investment comes at a time when Bharti, like several Indian telecom companies, is struggling with falling profits due to high interest costs and intense competition in the country.
Bharti reported Thursday that its net quarterly profit halved in the first quarter of the calendar year compared with 2012 to 5.08 billion rupees ($94 million), the 13th straight quarterly fall in its profitability.
News of the new investment encouraged investors, however, with Bharti shares rising as much as 4.5 percent to a high of 331 rupees on the Bombay Stock Exchange, after the news.
"This strategic partnership with QFE demonstrates the confidence they have in us and our strategy for growth," said Bharti's chairman Sunil Mittal.
QFE's acting chief executive Rashid Al-Naimi said as a long-term global investor, the shareholding gave them "exposure to a high growth sector in key emerging markets".
Analyst Ankita Somani of Mumbai's Angel Broking said the stake sale will help Bharti to reduce its debt, estimated at $11.74 billion at the end of March.
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