Tanzania’s leading opposition candidate is rejecting Wednesday’s presidential vote after alleging widespread irregularities, saying that whatever happened was not an election and was like “spitting in the face of democracy."

Tundu Lissu of the CHADEMA party also appeared to warn of unrest: “Those in power are telling Tanzanians, ‘If you want change, look for it another way, not through the ballot box, not through democracy,’” he told reporters Thursday. “The message they are sending is, ‘Use force if you can ... We won't let you win through democracy. If you want, use force.'"

Lissu asserted that thousands of observers were turned away from polling stations and those who managed to enter were not given official results.

The other top opposition party, ACT Wazalendo, announced that its presidential candidate in the semi-autonomous region of Zanzibar, Seif Sharif Hamad, was arrested Thursday for the second time in a week.

The East African nation’s electoral commission has denied allegations of irregularities as populist President John Magufuli seeks a second five-year term. Results could be announced as soon as Thursday.

Tanzania Elections Watch, a regional group of eminent persons, expressed concerns about the conduct of the vote.

“Unfortunately, in Tanzania the announcement made by the National Electoral Commission is final,” the group's co-chair Frederick Ssempebwa told a briefing, as results cannot be challenged in court. “There is no avenue for the aggrieved parties to air their views.”

The declaration of results could trigger a wave of instability, Ssempebwa said.