Tanzania's populist president John Magufuli was declared the overwhelming winner of the elections by the National Electoral Commission on Friday, sparking a backlash by the opposition who allege fraud.
Magzfuli's victory means he will run for a second term and the ruling party CCM, which has been in power for decades, won enough seats in parliament to change the constitution.
Some in the ruling party had called for the presidency's two-term limit to be extended if enough parliament seats could be secured.
The electoral body said Magufuli won 84% of the vote while his main rival Tundu Lissu of the Chadema opposition party received 13%.
Lissu has rejected the result and called for peaceful protests and action.
"The results that have been announced since yesterday and that the electoral commission continues to announce today, therefore, are illegitimate results. They do not constitute, they do not express the true will of the Tanzanian people," Lissu said.
Lissu called for peaceful protests and action.
The US embassy in Daar el Salam said while the vote went peacefully, there were credible allegations of significant election-related fraud and intimidation.
"There is a lot of complaints about the irregularities during the elections like fake ballot papers, but our leaders have forced their will on us, along with the police," said Chadema supporter Amani Saria.