There was violence in April, as voters lined up to register

The Civic United Front (CUF) says it will launch a revolution as seen in Ukraine last year if its complaint are not dealt with before October's polls.

Developing a voters' roll that could be checked independently was part of an all-party pact to stop poll violence.

The CUF accused the ruling CCM party of rigging the 2000 elections.

'Evidence'

The CUF condemned the "breaching" of the contract with the South African company by the island's electoral board.

We shall use people power without causing any violence like our colleague in Ukraine to fight for our rights CUF's Ismail Jussa

The government cited procedural reasons for suspending the contract.

"This is evidence of the ruling party trying to rig the election," CUF official Ismail Jussa said.

"We shall use people power without causing any violence like our colleagues in Ukraine to fight for our rights," he told AFP news agency.

The opposition enjoys most of its support on the semi-autonomous archipelago but the CCM party has won recent elections on the islands as well as on mainland Tanzania.

Some 40 people were killed in violence during the 2000 election campaign.