COLOMBO (Reuters) - The Maldives will hold presidential elections on September 7, officials said, spurning calls for an earlier vote and risking further protests by supporters of ex-president Mohamed Nasheed who says he was overthrown in a coup last year.

Nasheed's followers have already taken to the streets several times since his departure amid political turmoil that has threatened the Indian Ocean nation's key tourism industry.

Nasheed, the islands' first democratically elected leader, left office in contested circumstances in February last year - he says he was forced out at gunpoint while his successor President Mohamed Waheed Hussain Manik says he left voluntarily.

On the eve of the anniversary of that power transition, presidential spokesman Imad Masood said on Wednesday the elections commissioner had chosen Sep. 7 as the date for the next vote.

Nasheed's Maldivian Democratic Party has already approved his candidature in the next vote.

But he is facing a court case relating to the detention of a judge during the last days of his rule and could be barred from standing if found guilty.

He has accused the authorities of harassing his supporters and had called for new elections in 2012 in the country that sits on busy shipping lanes and has increasingly become a target for Somali pirates.

The Maldives, for almost nine centuries a sultanate before it became a British protectorate, held its first free elections in 2008. Nasheed defeated Maumoon Abdul Gayoom, who was then Asia's longest-serving leader and accused of running the country as a dictator/

President Waheed had earlier said the election could not be held any sooner than July 2013 but did not mention a specific date.

(Reporting by Shihar Aneez; Editing by Andrew Heavens)