Kuala Lumpur, Aug. 17 (Bloomberg) -- Telekom Malaysia Bhd., Malaysia's biggest phone company, said it will buy an additional 15 percent stake in Ghana Telecommunications Co. for $100 million to help boost its earnings through overseas investments.

Telekom signed a pact on Aug. 11 to acquire the stake from the government of Ghana, the company said in a statement. Telekom, through its 85 percent-owned unit in Ghana, already owns 30 percent in Ghana Telecommunications. The balance 70 percent of Ghana Telecommunications is owned by the government of Ghana.

Following the transaction, Telekom's stake will rise to 45 percent, while the government's stake in Ghana Telecommunications will be reduced to 55 percent.

Ghana Telecommunications, which controls 73 percent of the fixed-line business in the African nation, will soon unveil its mobile phone and public payphone services in that country, Telekom said.

Telekom is expanding abroad as it looks to reverse a slump in earnings.

The Malaysian company's earnings have declined every year for the past three years as rising competition chipped away its share of Malaysia's 13 billion ringgit-a-year telecommunications industry.

The announcement came after the market closed.

Telekom shares rose 50 sen, or 4.6 percent, to 11.50 ringgit.