The main battle for votes is being fought in Zanzibar

Tanzania's postponement was due to the death of Chadema's vice-presidential candidate, Jumbe Rajab Jumbe.

The Zanzibar Election Commission said the semi-autonomous archipelago had different electoral rules.

Earlier, Chadema's presidential candidate critised the length of the delay accusing the ruling party of making politcal capital out of it.

Heavy security

Tanzania delayed national presidential, parliamentary and local elections on Thursday, but there was uncertainty overnight about whether the polls on Zanzibar and Pemba would proceed.

[The ruling party] are going to have a win-win situation Chadema's Freeman Mbowe

But electoral commission official Swaleh Yusuf told the BBC that Zanzibar was not bound by national electoral rules and voting would go ahead.

There has been a hotly contested campaign on the islands and several violent incidents have been reported.

In one incident a gang of youths attacked a former presidential bodyguard and in another, three people were injured when young men tried to prevent supporters of the opposition Civic United Front (Cuf) putting up posters of their candidate.

The BBC's Noel Mwakugu in Zanzibar said security has been stepped up ahead of voting.

In a bid to calm tension, the Zanzibar Electoral Commission announced on Thursday it had struck off the voters' roll the names of 2,000 people who had registered twice.

Cuf accuses Zanzibar's governing Chama Cha Mapinduzi (CCM) party of planning to rig the ballot.

Cuf maintains that it has been cheated of victory in Zanzibar - its main power base - in the past two Tanzanian elections, in 2000 and 1995.

'No money'

On the mainland, the CCM is expected to maintain its grip on power, with its presidential candidate Jakaya Kikwete tipped to succeed outgoing President Benjamin Mkapa who steps down after two terms in power.

Jakaya Kikwete is tipped to be Tanzania's next president

According to Tanzania's National Electoral Commission, Chadema has until 18 November to decide on a new vice-presidential candidate, when campaigning will start again.

But Chadema's presidential candidate, Freeman Mbowe, said a week's delay would have sufficed and his party cannot afford to finance extra campaigning.

He told the BBC's Network Africa programme that the commission took the decision to halt national polls to favour the ruling CCM.

"It's going to harm my chances; it's going to harm all opposition parties chances and work in favour of the ruling party," he said.