MARIKANA, South Africa--South African retailer Massmart Holdings Ltd. (MSM.JO ) Wednesday reported a rise in full-year sales and profit and said it plans to open 40 new stores over the next 18 months, despite a pressure on margins, as it seeks to boost market share following its integration with U.S.-based Wal-Mart Stores Inc. (WMT)

Sales rose 16% to 61.2 billion rand ($7.39 billion) while headline earnings, a common measure of profit in South Africa that strips out some items, was up 8.9% to ZAR1.36 billion in the year ended June 24. The company is in the process of aligning its earnings report to the Wal-Mart financial year that ends in December.

Earlier this year, Wal-Mart completed a deal to buy a majority stake in Massmart. Chief Executive Grant Pattison said the integration should boost profit at Massmart from 2014, when the integration process is complete. In the meantime, the company is focusing on growing sales and market share and opening new stores.

The company has already invested ZAR1.7 billion rand on infrastructure and building 25 new stores in the year and will spend ZAR2.6 billion in capital on opening 40 new stores. The company said it has targeted about 15 sites in parts of Africa it wants to add stores in but needs to secure property rights. Mr. Pattison said the company has approved store openings in Kenya and Angola and plans news stores in Mozambique and Zambia over the next year. He said the companies want to take the model of discount supermarkets to west and east Africa.

Wal-Mart's entry into South Africa was viewed as a spring board for growth into the rest of the continent, which is pinning better economic growth than many parts of the world.

Difficulties in securing property rights in the rest of Africa has, however, slowed the company's expansion down but Mr. Pattison said Massmart should open five new stores in the next 18 months outside of South Africa.

"With the new relationship with Wal-Mart I think we are positioned for significant market share growth over the short term," Mr Pattison said. He said, however, that Wal-Mart's ability to source goods cheaper than anyone else has been "overestimated."

While Massmart is pushing ahead on expansion, it warned that middle income consumers -- some of its core shoppers in South Africa -- are coming under pressure. Inflation in the past financial year rose 1.8% and Mr. Pattison said over the next 18 months it will increase particularly given the shortage of corn.

"Net margins won't rise over the next 18 months but we will focus on growing sales and market share," Mr Pattison said.

Write to Devon Maylie at devon.maylie@dowjones.com