NOUAKCHOTT, June 29 (Reuters) - Mauritania's President Mohamed Ould Ghazouani opened an early lead as vote-counting started after Saturday's presidential election, provisional results from the country's electoral commission showed.

With around 4.37% of votes counted, or just over 200 polling stations out of 4,503, Ghazouani was leading with 45.95%, while his main rival, anti-slavery activist Biram Dah Abeid, was at 24.64%, Mauritania's electoral commission said. (Reporting by Kissima Diagana Writing by Bate Felix; Editing by Chizu Nomiyama)