NAIROBI (Reuters) - Hilton Worldwide Holdings (HLT.N) plans to more than double its hotels in Africa in the next five years by mainly striking deals with existing hotels for conversion into its brand, its chief executive said.

International chains, including Marriott International (MAR.O) and Hyatt Hotels (H.N), have been increasing their investments in Africa, which has some of the world's fastest growing economies and a rising middle class.

Hilton plans to introduce its Curio Collection, an upscale hotel brand, on the continent, starting with a hotel at Lagos airport in Nigeria, Chris Nassetta, the company's president and CEO, said.

"This hotel is a part of our strategy to connect guests to key cities and airport locations across the region," he said in a statement issued on the sidelines of a hotel industry meeting in the Kenyan capital.

The continent continues to undergo rapid urbanization, with the United Nations forecasting that the world's 10 fastest-growing cities will all be in Africa by 2035, he said.

"Hilton is seeing strong demand for its brands across the continent and expects to open eight hotels in total across Africa this year," the company said.

The Mclean, Virginia-based firm has operated in Africa, where it has 41 open hotels and 53 in development, since 1959.

The pipeline of new facilities is part of its Africa growth initiative, launched last year, which involves the investment of $50 million over five years.

It will result in Hilton starting operations in countries where it does not have a presence such as Botswana and Rwanda.

Other big international hotel groups, including Radisson and Kempinski, are estimated to have about a third of the available room capacity on the continent.

The rest are independently-run hotels, offering opportunities to global operators to strike deals with their local counterparts, industry executives say.

(Reporting by Duncan Miriri; editing by David Evans)