President Samia Suluhu Hassan had sought to solidify her position and silence criticism within her party in the virtually uncontested polls, with the main challengers either jailed or barred from standing
But election day descended into violence as hundreds took to the streets.
An AFP journalist saw a police station burned down in the economic hub, Dar es Salaam, and there were reports of polling stations being attacked and protesters tearing down images of the president in several parts of the country.
A diplomatic source told AFP they had unconfirmed reports of 30 or more people killed.
But a full internet blackout remained in place on Thursday, along with limits on international calls, making verification all but impossible.
Almost all foreign journalists had been barred from entering the country for the election
The heavily controlled local media had made no updates to stories since early Wednesday.
Schools and colleges were closed on Thursday, and civil servants were told to work from home, an AFP reporter said, adding that gunshots could still be heard across Dar es Salaam.
