Telecom czar Sunil Mittal-led Bharti Airtel's Africa unit plans to launch over USD 1 billion (around Rs 6,970 crore) IPO in London to help reduce debt. The firm plans to sell 25 per cent of new shares of Airtel Africa in the proposed initial public offering (IPO) and is looking to trade on the main market of the London Stock Exchange using its premium listing segment, Bharti Airtel said in a regulatory filing. It is also considering a listing in Nigeria, the firm added.