Bharti Airtel’s UK subsidiary Airtel Africa on Wednesday announced that a group of six global investors led by Warburg Pincus, Temasek, Singtel and SoftBank Group International will invest $1.25 billion (around Rs 9,141 crore) through a primary equity issuance in the company, the proceeds from which will be used to retire part of its around $5-billion debt and for expanding operations.