Former Nigeria President, Goodluck Jonathan, is leading a team of the African Union (AU) Expert Election Observers to monitor election in Tanzania.
Confirming the report, Jonathan said the team visited some polling stations in Dar-es-Salaam on Wednesday morning as voting got underway.
He said the African Union saw the Wednesday polls as yet another opportunity for the good people of the United Republic of Tanzania to deepen democracy and peace in the country.
Polls have opened in Tanzania’s general election, following nationwide reports of restricted internet access plus the arrest of an opposition leader in the semi-autonomous islands of Zanzibar.
Voters have until 16:00 local time (13:00 GMT) to cast their ballot.
Results are expected to be announced within one week.
President John Magufuli, whose Chama Cha Mapenduzi (CCM) party has ruled Tanzania since independence in 1961, is seeking a second term in office.
His main challenger is Tundu Lissu of the biggest opposition party, Chadema, who survived an assassination attempt three years ago.
He returned from Belgium in July where he had undergone rounds of treatment for gunshot wounds.