The IPO could be one of the biggest this year in London, where lackluster domestic volumes are being boosted by emerging-market companies seeking a wider investor pool. Finablr, the currency-exchange firm controlled by an Abu Dhabi-based billionaire, starting taking orders last week for a share sale that could raise as much as $677 million. Middle Eastern payments processor Network International Holdings Plc raised 1.1 billion pounds ($1.4 billion) last month in the largest London IPO this year.

Valuation and the listing date are still under discussion, and final details could change depending on investor demand and market sentiment, the people said. A representative for Bharti Airtel declined to comment.

Bharti Airtel, backed by billionaire Sunil Mittal, has spent heavily to defend its position in India against disruptive upstart Reliance Jio Infocomm Ltd. The firm’s Africa unit raised $1.25 billion last year from investors including Temasek Holdings Pte and SoftBank Group Corp., giving it an equity value of about $4.4 billion.

The business has operations in 14 African markets including Kenya, Tanzania, Nigeria and Ghana, according to Bharti Airtel’s latest annual report.