The next president must come from the island of Anjouan
Comorans vote on 16 April in the first round of a presidential election which observers see as a key test of whether, after three decades of instability, the Indian Ocean archipelago can make the transition to peaceful political change.
What's at stake?
Since independence from France in 1975, the country has witnessed 20 coup attempts - four of them successful - often involving foreign mercenaries, as well as bitter inter-island strife and assassinations.
Western observers have described the polls as a turning point, with a successful election being seen as a test of Comoros' power-sharing arrangements and its quest to end its image as a chronically unstable country.
The people of the Comoros are among the poorest in Africa and are heavily dependent on foreign aid.
Concerns have been expressed that if the international community does not consider the polls to be largely free and fair, it could delay the disbursement of aid worth some $200 million pledged as part of a three-year development plan in 2005.
What's the political system?
Under the constitution and political agreements reached in 2001, the Union presidency rotates every four years between Comoros' three semi-autonomous islands - Grande Comore, Anjouan and Moheli.
President Azali Assoumani, from Grand Comore, won the first election in 2002 after coming to power via a bloodless coup three years earlier. In mid-2005, he tried unsuccessfully to change the rules and stand for a second term but is ineligible to run.
It is now Anjouan's turn to hold the presidency and on 16 April its voters will short-list three candidates who will go on to stand in national elections on 14 May, in which voters from among the population of all 670,000 Comorans will vote.
The union president has two deputies who must not come from the same island as the president.
Who is watching the polls?
The elections are being carefully scrutinised by Comoros' neighbours, in particular South Africa, as well as by the African Union (AU) and Arab League.
South Africa is leading a 460-strong AU mission which began operations in the capital Moroni on 30 March.
The mission consists of civilian and military police to provide security, as well as poll observers. One of its key is to ensure that Comoran troops do not interfere in the voting.
The government has ordered its soldiers to remain in their barracks.
France has pledged 1.2m dollars to be channelled through the UNDP.
Who are the candidates?
The elections are overseen by the Comoros National Electoral Commission.
The authorities have cleared 13 candidates for the Anjouan primaries, including veteran politicians, former military officers and prominent Islamists. For the first time, the candidates are accompanied by their running mates and the polls are also the first to feature women candidates.
Observers view the high number of candidates as a sign of a tight race.
The candidates include:
Caabi Mohamed El-Yachroutu who has held several top positions such as prime minister and union vice president; he is said to have close ties with ex-colonial power France and international donors.
Ahmed Abdallah Mohamed Sambi, an Islamic preacher and former MP; he owns a radio and television station in Anjouan which he is using to support his candidacy.
Abderemane Ibrahim Halidi, a former prime minister and teacher from the deprived region of Nioumakele in Anjouan; he is being supported by the incumbent president and his party, the Convention for the Restoration of Comoros.
What happens on voting day?
On 16 April, some 120,000 eligible voters from a population of 270,000 on Anjouan will cast their ballots at 222 polling stations.
The polls open at 0700 (0400 GMT) and close at 1800 (1500 GMT), although the electoral commission has said the closing time may be extended.
Preliminary returns could be announced the same evening but final results are not expected until the Constitutional Court validates the tally on 19 April.
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