Zanzibar's president and vice president, who currently rule together in a government of national unity, go head-to-head in the archipelago's presidential race on Sunday October 25, 2015.

President Ali Mohamed Shein from Chama Cha Mapinduzi (CCM) is running against his first deputy, Sief Sharif Hamad, from the opposition Civic United Front (CUF).

The CCM has promised to maintain Zanzibar's semi-autonomus status, but the CUF says it will push for full autonomy if it wins.

Zanzibar experienced a brief period of independence in early 1964 before merging with Tanganyika to become part of Tanzania.

CCM's Shein polled 50.1 percent of the vote and CUF's Hamad secured 49.1 percent at elections in 2010.

65-year-old Mzee Haidar Madoweya is a supporter of the CCM which has been in power since 1977.

"I believe we have reached our voters with a simple message 'mbele kwa mbele' (move forward) and when entering their polling stations they will surely remember that the country has to move on with the party that has been within them since independence," he said.

'Full sovereignty'

Zanzibar has been ruled by a CCM-CUF national unity government for the last five years. CUF supporters believe their party has been able to use this period as the junior partner in government to flag up their stance on Zanzibar's relations with mainland Tanzania.

Sultan Riyami, a CUF supporter, highlighted his party's commitment to complete autonomy for Zanzibar. He stressed that the CUF had "managed to form a government of national unity and changed our constitution to categorically declare our Zanzibar a country." The next stage, he claimed, would be "full sovereignty."

Uneasy calm?

Zanzibar has experienced sectarian and political tensions in recent years and there is some pre-election nervousness.

Hamad, the CUF's contender, has said he is concerned about possible violence after clashes between young supporters of rival parties during campaigning. "Our fear is that once again there are signs that the ruling party, CCM is planning to cheat," he said in a recent speech.

Shein, the incumbent president, has accused the CUF of threatening not to accept defeat if they lose and of issuing misleading campaign statements.

Zanzibari police chief Hamdan Omar Makame told AFP "peace has prevailed ahead of the elections" with only a "few reports" of attacks.

In addition to the two main candidates, there are 12 other contenders, vying for the support of Zanzibar's half a million voters.

Mainland Tanzania also faces a tight race on October 25 with the CCM's John Magufuli facing a stiff challenge from opposition candidate Edward Lowassa.

Mohammed Khelef contributed to this report