Voters in Ethiopia's Sidama region went to the polls a day late on Tuesday as officials counted ballots from other regions in an election marred by an opposition boycott, war and reports of irregularities in some areas.

Prime Minister Abiy Ahmed hopes the national and regional elections will show the success of democratic reforms he launched after being appointed by the ruling coalition in 2018.

But the vote also reflects a messy reality in the country of 109-million people. Authorities could not hold polls on Monday in four of Ethiopia's 10 regions including Sidama, where there were logistical problems, according to the election board.

"Democracy is not built in a day. We are laying it brick by brick," Abiy said in a written statement late on Monday.

"No matter who wins, Ethiopians from all over the country have voted for whomever they choose, without any fear and without any kind of pressure. And because of that, Ethiopia is triumphant," said Abiy.

There was no comment from him on Tuesday morning and his spokeswoman did not immediately respond to a request for comment as counting proceeded.

In two regions where voting did happen, opposition observers were reportedly chased away from many polling stations, board chief Birtukan Midekssa told reporters late on Monday. The board was scheduled to hold a news conference at 2 pm (1100 GMT).

Abiy's newly formed national Prosperity Party is widely forecast to defeat the fragmented opposition of dozens of mostly ethnically based parties. The ruling coalition and its allies hold all 547 national parliamentary seats.

Though the prime minister won the Nobel prize in 2019 for making peace with neighbouring Eritrea, his international reputation has been tarnished since conflict erupted in the northern Tigray region in November.

Fighting between Ethiopia's military and the region's former governing party, the Tigray People's Liberation Front (TPLF), has forced more than 2-million people from their homes, and the United Nations reports there is a famine looming. No date has been set for elections in Tigray.

The opposition alleged some irregularities in regions that voted.

Opposition leader Berhanu Nega said his Ethiopian Citizens for Social Justice party (Ezema) had filed 207 complaints after local officials and militia in Amhara region and in the Southern Nations, Nationalities, and Peoples' Region, blocked party observers, he said.