Magufuli -- pictured on a campaign billboard for the 2015 president elections -- has been accusing of seeking to muzzle dissent
Dar es Salaam (AFP) - Tanzania's ruling party candidate John Magufuli won hotly contested presidential elections, officials announced Thursday, but the opposition said the vote was rigged and also claimed victory.
The win by Magufuli with over 58 percent of votes cements the long-running Chama Cha Mapinduzi (CCM) party's firm grip on power, ruling Tanzania since 1977 when two independence-era parties merged.
But tensions are high amid deep concern at opposition claims of rigging, as well as the semi-autonomous Zanzibar archipelago's decision to annul polls.
"I duly declare John Pombe Magufuli to have been duly elected President of the United Republic of Tanzania," National Electoral Commission (NEC) chief Damian Lubuva announced.
His running mate Samia Suluhu Hassan will become Tanzania's first ever female vice president.
"He is the right person for our country," said outgoing President Jakaya Kikwete, who steps down after serving his two-term limit.
Outside CCM party headquarters, supporters danced in the streets, waving flags and shouting Magufuli's name.
Magufuli, a former chemistry teacher who also celebrates his 56th birthday on Thursday, ran on an anti-corruption platform, and secured a convincing victory over his closest rival, ex prime minister Edward Lowassa who won 40 percent.
Lowassa, a former CCM stalwart turned opposition chief, rejected the official results and accused the election body of falsifying tallies.
"We refuse to accept this attempt to rob the citizens of Tanzania of their democratic rights, which is being done by the National Electoral Commission by announcing results which are not the actual results," Lowassa told reporters.
"We are requesting that the National Electoral Commission announces that Edward Lowassa is the winner of the presidency," he said.
Lowassa, 62, was prime minister from 2005 until his resignation in 2008 over corruption allegations that he denies, and has for years been a CCM loyalist, but on the campaign trail he called for an end to the party's rule.
- Zanzibar vote annulled -
International observers, including from the African Union and European Union, said the polls were carried out in a "competent and largely efficient" manner.
"We were pleased that the voting and counting took place in an atmosphere of peace, and that the people of Tanzania demonstrated a strong commitment to their democratic process by turning out in significant numbers to cast their vote," a joint statement from African and other international observers read.
The elections, held on Sunday, were the hardest fought electoral race in the east African nation's history, with the opposition providing the first credible challenge to the CCM since the introduction of multi-party democracy in 1995.
While the CCM celebrated Magufuli's win, and have also secured an overall majority in parliament, victory came at the cost of several veteran CCM ministers and politicians, ousted from their parliamentary seats.
"We are pleased with the results and thank Tanzanians for the trust," top CCM official January Makamba said. "It is a big debt and our government will deliver on our election pledges."
The results included votes from the semi-autonomous Zanzibar archipelago, despite the electoral commission on the islands having annulled polls over irregularities.
Zanzibar's electoral commission said the islands' vote -- where the 500,000 registered electorate also voted for Tanzania's national president -- must be carried out again, citing "violations of electoral law".
African and other international observers in Tanzania said they were deeply concerned at Zanzibar's annulment, urging leaders to "cast aside their differences" to ensure peace.
"Democracy, peace and unity in Zanzibar are at stake," said a statement by international election observers, including teams from the African Union, headed by former Mozambican president Armando Guebuza, the Commonwealth, headed by former Nigerian president Goodluck Jonathan, and the European Union.
The United States embassy in Dar es Salaam said in a statement it was "gravely alarmed" and called for the annulment to be recalled.