Concerns for Zanzibar's crucial tourist sector have been reignited by the threat posed by Islamist secessionists, following rioting and the arrest of 51 supporters of Muslim cleric Sheikh FaridHadi on 18 October 2012.
The unrest, the latest in a series of violent protests since May, could also undermine the archipelago's fledgling oil and gas sector by complicating efforts by the oil industry to obtain exploration licences.
The violence was triggered by the unexplained disappearance of Hadi, who leads the Uamsho movement, a banned radical Islamist group that campaigns for Zanzibari independence from mainland Tanzania.
The roundup of his supporters followed two days of riots and looting in the commercial and tourist capital Stone Town. Although Hadi was later released by police without charge, the mass arrests will heighten tensions across Zanzibar, with further street protests in the coming weeks and months likely.
Since May 2012, Zanzibar has experienced a series of violent protests by Islamists amid a growing secessionist movement. While the islands enjoy semi-autonomous status and are governed by their own parliament and president, supportfor full independence from mainland Tanzania is mounting among youths and the urban poor.
Hitherto largely marginalised as a group of radicals, Uamsho has steadily gained greater public acceptance since the Zanzibar opposition party Civic United Front controversially entered intoa coalition governing the autonomous region in 2010 with the mainland ruling party, Chama Cha Mapinduzi.
A growing sense of disenfranchisement from the political process combined with high youth unemployment has contributed to the rejection of mainstream secular parties. Meanwhile, high levels of inequality persist in Zanzibar despite the vast profits enjoyed by the tourism sector.
Mainland Tanzania, led by the secular Jakaya Kikwete government, has also experienced a recent upsurge in religious tensions. On 19 October 2012, Islamists in the capital Dar es Salaam staged a violent protest to demand the release of the Muslim cleric, Sheikh Issa Ponda.
Although Ponda is not believed to hold direct connections with Uamsho, the crowd also took the opportunity to protest Hadi's detention in a bid to draw parallels between the alleged targeting of Islamists by the state.
Akin to unrest in Zanzibar, high levels of youth unemployment, economic inequalities and a rejection of mainstream secular parties are contributing to malaise on the Tanzanian mainland.
Uamsho's expanding support base has heightened sectarian tensions despite years of peaceful coexistence between Zanzibar's Muslim majority and Christian minority, with several churches targeted in recent months.
Tourism and business stakeholders are particularly concerned as the group's ascendency has also coincided with attacks against bars and other tourist targets.
Yet despite pledges to safeguard the tourist sector, the authorities appear incapable of stemming the wave of violence. For instance, a minister in 2011 publicly threatened the arrest of non-Muslims found eating in daytime hours and female tourists dressed inappropriately during the holy month of Ramadan.
A major concern for Zanzibar's lucrative tourist industry will be the reputational damage from the latest violence. While tourists were not directly caught up in the riots, the immediate impact was road closures in a key tourist hub, as well as widespread panic. Tourism is the dominant source of revenue in Zanzibar, accounting for some 27% of the island's gross domestic product, according to the Finance and Economy Ministry. In fact, the figure is likely to be significantly higher when unofficial revenues are taken into account.
In the longer term, the secessionist movement is likely to complicate efforts by the oil industry to obtain licences for exploration off Zanzibar's coastline.Tanzania is set to become a major new gas frontier following a series of discoveries off the East African seaboard, with government estimates of recoverable natural gas reserves of up to 22 trillion cubic feet.
However, a dispute over how to split potential revenue from four hydrocarbon blocks off the Zanzibari coastline has stalled exploration work.
While the mainland government is pushing for exploration to go ahead with the national treasury to administer revenue, Zanzibar wants profits to go directly to islanders. The dispute could also complicate central government plans to amend oil industry legislation by the end of the year, dampening investor confidence in the country's nascent oil industry.
With tensions heightened on multiple fronts, further unrest is anticipated in Zanzibar in the coming months. Although tourists are unlikely to be targeted directly, there is a risk of collateral damage. In the short term, the convergence of various marginalised groups in the protest movement is likely to destabilise the Zanzibar government, even if radical Islamist rhetoric and secessionism ultimately relate to separate motivations. In the longer term, the matter of independence will dominate the political debate in view of plans by the mainland government to finalise a new constitution by 2014.
While there is little risk of Zanzibar's tourism revenue drying up, simmering unrest may see reduced numbers of arrivals, with some of the larger tourist operators choosing alternative destinations. Meanwhile, the government may prefer to delay the all-important decision over revenue sharing from Zanzibarioil blocks until other constitutional issues are finalised, prolonging uncertainty for foreign investors.
Sarah Tzinieria is Senior Africa Analyst at Maplecroft