WINDHOEK (Reuters) - Namibia's Nangolo Mbumba, who took over as interim president of the southern African country on Sunday after Hage Geingob died in office, said he had no plans to run in elections due at the end of the year.

       That means Netumbo Nandi-Ndaitwah, who replaces Mbumba as vice president and was nominated by the governing South West Africa People's Organisation (SWAPO) just over a year ago to be its candidate, will remain on the ballot.

       If she wins, she will be the southern African nation's first female president.

       "I am not going to be around for the elections so don't panic," Mbumba said in a move that is rare among African leaders who have often sought to retain power once it is in their hands.

       "My aim was to be a school principal, which I achieved and now I have to thank the Namibian people for the honour they have bestowed on me to be their president, for a short period," Mbumba said at his swearing-in ceremony.

       SWAPO's constitution forbids making changes once the candidate has been picked two years before the poll is due.

       The party has ruled Namibia - a mining hotspot with abundant diamonds, uranium and also lithium needed for electric car batteries - since independence from South Africa in 1990.

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       Geingob, in power since 2015, died aged 82 in the early hours of Sunday after a brief battle with cancer.

       "It is poignant and reassuring to note that today, even in this time of heavy loss, our nation remains calm and stable," Mbumba said. "This is owing to the visionary leadership ... of president Geingob who was the chief architect of the Namibian constitution."

       Geingob leaves behind a middle-income country fighting to push economic growth above 3% following a pandemic-era slowdown and reverse racial inequalities left over from colonialism and annexation by South Africa's former white minority government.

       He led Namibia's efforts to recast itself as a leader of the global green economy and in 2022 Namibia became the first African country to agree to supply the European Union with green hydrogen and minerals needed for clean energy.

       Last year, Namibia began constructing Africa's first decarbonised iron plant, to be powered exclusively by green hydrogen - which is extracted from water using electrolysis powered by renewable energy - blazing a trail in the reform of steelmaking, one of the world's most polluting industries.

       These developments put Namibia ahead of its economically bigger and more industrialised neighbour South Africa, whose green energy transition efforts have been faltering.

       (This story has been refiled to fix Nangolo Mbumba's name in paragraph 2)

       (Reporting by Nyasha Nyaungwa; Writing by Tim Cocks; Editing by Emelia Sithole-Matarise)