(Adds details from official)

TUNIS, Aug 30 (Reuters) - Tunisia's state-run Gafsa Phosphate company has suspended all production because of protests demanding jobs at its three main sites that will impact its exports, an official at the operation said on Tuesday.

Once one of the world's largest producers, Tunisia has seen its market share fall after its 2011 uprising against Zine El-Abidine Ben Ali. Since then protests and strikes have steadily cut into production and caused billions of dollars in losses.

"Gafsa phosphate production is completely halted after sit-in protests by jobless people demanding work," said company official Ali Houchati. "This is going to hit exports quickly because there are not that much reserves."

Tunisia produced about 8.26 million tonnes of phosphate in 2010. But it produced 4 million tonnes last year and output for the first six months of 2016 was 1.86 million tonnes, according to the energy ministry.

The renewed Gafsa protests will be one of the first tests for the new government of Prime Minister Youssef Chahed who last week said he would take a strong position against sit-ins that damaged the country's economy.

Tunisia's democratic progress since the 2011 uprising has been praised as a model for the region. But Islamist militant attacks have hit its key tourism industry - a major revenue source.

(Reporting by Tarek Amara; writing by Patrick Markey; editing by Susan Thomas) ((pat.markey@thomsonreuters.com; +213-661-692993; Reuters Messaging: pat.markey.thomsonreuters.com@reuters.net))