DAR ES SALAAM, Tanzania (AP) — Tanzanians are voting in general elections in which the ruling party faces a strong challenge from a united opposition.

In the presidential race, the ruling party's candidate, John Magufuli, is battling former Prime Minister Edward Lowassa, who defected to the opposition earlier this year after being rejected as the ruling party's candidate.

Lowassa, 62, was prime minister in President Jakaya Kikwete's government from 2005 to 2008, but was forced to resign by a corruption scandal.

Magufuli, 55, is widely seen as a corruption-free, effective public servant who could improve the ruling party's image in the eyes of ordinary people fed up with state graft.

Voters Sunday are also choosing lawmakers for the country's parliament and local officials.

In Dar es Salaam, the largest city, there were long lines at polling centers, as well as a heavy security presence. Many in the lines were young people.

"This is going to be a tight race, if this turnout is anything to go by," said Dar es Salaam resident Amina Abdallah, one of those lining up to vote. "I just pray that it will be peaceful, so we can all go back to our normal life."

The electoral commission says it hopes to announce the winner within three to four days, although it has up to a week to announce the results.

Damian Lubuva, the commission's head, said Saturday that more than 23 millon voters are registered to vote across the East African country.

The semi-autonomous island archipelago of Zanzibar is also voting for a president and local leaders.