Nippon Telegraph & Telephone Corp. agreed to buy South Africa's Dimension Data PLC for £2.1 billion, or ¥286 billion, to expand in the faster-growing computer-services market, NTT said Thursday.

Japan's largest phone company offered 120 pence a share, or 18 percent more than Johannesburg-based Dimension's last closing price, the Tokyo-based phone carrier said. The management of Africa's largest computer-services company and a majority of its shareholders have agreed to the sale, it said.

The friendly buyout is expected to be completed in October, enabling NTT to expand its global operations for corporate customers, the Japanese telecom giant said.