Chadema party, Tanzania's main opposition party, said police on Monday had detained 40 volunteers who were monitoring the vote counting process. The incident puts a dent in an election largely viewed as peaceful. "Police also confiscated computers and mobile phones of our volunteers who were tallying results of the presidential election," John Malya, a Chadema lawyer, said.

The Civic United Front, another opposition party, said police had fired tear gas at a crowd of its supporters in Tanzania's Indian Ocean island of Zanzibar. CUF said the attack on its supporters was meant to "intimidate the opposition."

Apart from the semi-autonomous archipelago of Zanzibar which has often experienced violence during elections due to strong separatist sentiments, the East African nation of 52 million people remains one of Africa's most stable democracies.

Self-declared winner

Zanzibar's main opposition presidential candidate, Seif Sharif Hamad, who ran under CUF on Monday, declared himself the winner of elections in Zanzibar ahead of any official announcement of results.

Sharif Hamad told DW he had seen official documents of final voting figures and asked his opponent, Ali Mohamed Shein, to accept the people's verdict. ''We want the commission to announce the official results. But I urge Shein, to be a gentleman so as not to put the country into chaos,'' Sharif Hamad said. He said it was important to seek ways of diffusing the political tension in the country. ''The commission therefore should not do anything against the decision of the people. ''

The hotly contested race for the presidency has pitted John Magufuli of the ruling CCM against former prime minister Edward Lowassa, who for the first time is leading a united opposition.

Lowassa, who quit the CCM after the party overlooked him as their preferred candidate, said he would not concede defeat if he deemed the election as being not free and fair. "There are allegations of electoral fraud," Chadema spokesman Tumaini Makene told reporters late Sunday.

The opposition claims could not be independently verified. British High Commissioner Dianna Melrose said she was impressed with the way the election was conducted. "We witnessed thousands of people with high enthusiasm turning out and reporting at polling stations," Melrose said. "However, we are concerned with some cases where voting materials were delayed. This left many people frustrated."

CCM's election coordinator Yusuf Makamba warned the opposition against making "inflammatory statements" adding that such comments "may spark unrest."

Unfounded allegations?

Bana Benson, a political analyst in Dar es Salaam, told DW that allegations of voter rigging were unfounded. ''Generally the election has been conducted in a manner that is credible but every party has expectations. The opposition [Chadema] has invested a lot in terms of preparing candidates and they are gaining a number of seats," he said adding that it was still too early to talk of the presidential results.

According to provisional results which started trickling in on Monday , Magufuli was slightly ahead of Lowassa. Opinion polls and observers have predicted a win for Magufuli but expect the ruling party's parliamentary majority to dwindle considerably.

Benson said both Chadema and CCM parties managed to conduct successful campaigns. The two parties used the word "change" as their campaign tool. "The opposition capitalized on the fact that CCM has stayed in power for a long time and they thought it has outlived its usefulness," he said.

"On the other hand, the ruling party was a little bit fragmented, we have seen some of their strong cadres defecting to the opposition, however given its history and its organizational capacity, and they have managed to influence many voters. Many people think at the presidential level they have done very well."