Unrest has been a feature of Zanzibar's election campaign

Tanzania's semi-autonomous archipelago of Zanzibar is pressing ahead with presidential and legislative elections on Sunday despite the postponement of polls on the mainland.

While campaigning in the rest of the country has been peaceful, a series of violent clashes has marred the run-up to polling day in Zanzibar.

Why are the mainland polls being delayed?

Voters across the whole of Tanzania were to have chosen a new head of state and parliament on Sunday, with the incumbent president, Benjamin Mkapa, standing down after his maximum two terms.

But the National Electoral Commission announced a delay just three days before voting, following the death from illness of an opposition candidate for the post of vice-president, Jumbe Rajab Jumbe.

The elections are now scheduled for 18 December.

How will the elections work?

Zanzibar has its own electoral commission, which took the decision to go ahead with elections despite the delay on the mainland.

As well as casting their ballots for a president, voters will be choosing 50 members for the legislature and 139 local councillors.

But they will now have to wait until 18 December to vote in the nationwide elections.

Who is running for Zanzibar's presidency?

The current president, Amani Karume, is running for a second term after winning elections in November 2000.

The 52-year-old is a trained accountant, and served as trade and industry minister in the 1990s.

The eldest son of Zanzibar's first president, Mr Karume has vowed to preserve the existing relationship between Zanzibar and the mainland.

His main challenger is Seif Sharif Hamad, who was runner-up in Zanzibar's 1995 and 2000 presidential elections and complained of fraud on both occasions.

A teacher by profession, the 62-year-old hopes to increase the archipelago's control over its own affairs, although he is not seeking independence.

Four other candidates are contesting the election, but they are not expected to have a substantial impact on the outcome.

What are the main political parties?

Tanzania has dozens of political parties, but it is the top two that hold sway in Zanzibar.

Mr Karume's Chama Cha Mapinduzi (CCM) party has ruled the archipelago since it was founded in 1977, and also holds power on the mainland.

Zanzibaris will be voting weeks ahead of the mainland

Much of the CCM's support is drawn from mainlanders living in Zanzibar, as well as ethnic Africans.

The party portrays itself as a custodian of political stability and ethnic harmony, but has been accused by critics of engineering "racial animosity and flagrant political intrigues".

The Civic United Front (CUF) remains the largest opposition party in Zanzibar, where it has its headquarters.

Many of the party's followers are disenchanted Zanzibaris, mostly of non-African origin, and it also claims to enjoy the support of senior Muslim leaders.

With Mr Hamad as its presidential candidate, the CUF says it is the only party with a "credible, serious and authentic national leadership", but it has been accused of seeking to dissolve the union between Tanzania and Zanzibar.

What are the key issues?

Zanzibar's relationship with the mainland has been a source of political tension for many years.

Many Zanzibaris continue to have misgivings over the union, in the belief that the mainland benefits disproportionately.

The CUF does not back the idea of dissolving the arrangement, but some of its members have called for it to be reviewed. Mr Karume has promised to "consolidate the union and the Zanzibar Revolution".

The economy is also causing concern, with Zanzibar still largely dependent on spice exports. Unemployment is on the rise, particularly among young people.

A slump on the commodity markets has forced the government to diversify into tourism, but this move has been hampered by concerns among potential visitors about political instability.

There are also fears of a rise in religious intolerance.

What has happened during the campaign?

In a repeat of previous campaigns, the weeks leading up to Sunday's vote have been punctuated by a number of violent clashes, despite a joint statement from the leading candidates urging voters not to "awaken hatred".

Inflammatory speeches, suspicions about the transparency of the electoral process and general frustrations have been blamed for the violence, which peaked in August and early September.

Dozens have been left injured, houses and vehicles burned and campaign materials destroyed.

The identify of those responsible for fomenting the unrest remains unclear, but the leading political parties have been trading accusations.

Will there be observers?

A large number of local and international organisations are expected to send representatives to monitor the vote.

The authorities in Tanzania and in Zanzibar have encouraged observers to take part, but warned them to "adhere strictly" to electoral procedures.

Observers at previous elections in 1995 and 2000 declared those polls flawed.

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