By Devidutta Tripathy

Bharti Airtel Ltd has agreed to sell more than 3,500 mobile phone masts in six African nations to telecommunications tower firm Eaton Towers, in a deal sources said could be worth up to $800 million.

Bharti Airtel will lease back the towers from Eaton under a 10-year contract, the companies said in a statement on Monday. They did not disclose financial details.

Two sources with direct knowledge of the deal said the sale would be worth between $600 million and $800 million. One said the final price had still to be agreed before the two sides close the deal in the coming months.

Bharti Airtel, India's biggest telecoms group which operates in 20 African countries, is selling most of its more than 15,000 mobile phone masts there to cut costs. Maintenance is typically more expensive in Africa due to factors such as security costs and electricity shortages.

Bharti bought loss-making mobile phone operations in Africa from Kuwait's Zain in 2010, but has yet to turn a profit because of high operational costs and a heavy debt load.

In July, Bharti agreed to sell about 3,100 masts in four African countries to Helios Towers Africa.

The latest agreement with Eaton Towers for six countries includes Ghana, Uganda and Kenya but not Nigeria - Bharti Airtel's biggest African market - one of the sources said.

The sale of assets is positive for Bharti Airtel investors as it helps the company repay part of its debt load.

At the end of June, Bharti Airtel had a net debt of $9.6 billion, most of which was related to its $9 billion purchase of the African telecoms operations.

Bharti Airtel shares, valued at nearly $27 billion, closed 0.7 percent higher on Monday in a Mumbai market that rose 1.08 percent. The stock gained 8.5 percent last week.

Eaton Towers was founded by former telecoms executives in 2008 and started operations two years later. The Bharti deal will expand its footprint to seven countries in Africa and give it more than 5,000 towers.

Under the terms of the deal, Eaton Towers will also lease the former Bharti towers to other carriers, Eaton said. Eaton was advised by investment bank Moelis & Company in the deal.