Ethiopians are voting for a new parliament in the first election since the death of long-serving Prime Minister Meles Zenawi in 2012.
The current parliament has only one opposition MP – and Mr Zenawi’s successor Hailemariam Desalegn is expected to hold on to power.
The opposition and human rights groups have accused the governing party of intimidation – a criticism it rejects.
Observers from the African Union are monitoring the poll.
Polling stations opened at 06:00 (03:00 GMT) and close at 18:00 pm (15:00 GMT).
Hailemariam Desalegn on left, Debretsion Gebremikael (centre) and Tewodros Adhanom or right
Current Prime Minister, Hailemariam Desalegn (L), is favourite to retain the post but faces competition from leading challengers Debretsion Gebremikael (C) and Tewodros Adhanom (R)
Final results will not be known for a month.
Meles Zenawi’s Ethiopian People’s Revolutionary Democratic Front (EPRDF) has been in power for almost a quarter of a century.
More than 36m Ethiopians – and 57 political groups – have registered for the election. Many of them are organised along ethnic lines.
Other contenders include the Ethiopian Federal Democratic Unity Forum, a coalition known as Medrek [the Forum] and the Semayawi [Blue] Party, which has held protest rallies and draws support from young people.
Chart showing ethnic groups of Ethiopian population
Ethiopia has more than 80 different ethnic groups
“The government people came to go door-to-door asking us to register as voters and to promote the EPRDF,” Reuters news agency quoted a student as saying. “For me, all I see is that prices increase.”
Another voter told AFP: “I will give my vote to the ruling party because I do not have faith in the opposition parties’ ability to govern.”
Ethiopia has one of Africa’s fastest growing economies – with government-financed investments extending to new railways, roads and hydro-electric dams.
People take part in a Blue Party election rally in the capital Addis Ababa on 21 May.
Many young people have taken part in protests called by the Semayawi (Blue Party)
But critics accuse Prime Minister Desalegn of stifling dissent. One opposition candidate, Yilekal Getinet, said the government had closed political space.
Addis Ababa rejects the criticism. Government spokesman Redwan Hussein told AFP it was up to voters to choose.
“If they want to give us another chance they will vote for us. If they have a grudge, they will not.”
A general view shows part of the capital Addis Ababa on 17 May.
The government has invested massively in infrastructure projects
Predictions of another government success have turned some voters off the idea of casting a ballot. “The election will bring no change,” Behailu Ayele told Reuters. “It is already known that the EPRDF will win the vote like the previous elections – by fraud.”
In 2005, 174 opposition politicians won seats in the 547-seat parliament, but many did not take them up after pronouncing the vote rigged.
In the 2010 polls, Girma Seifu, of the Unity for Democracy and Justice (UDJ), was the sole opponent to win, while the EPRDF garnered 99.6%. An independent candidate was also elected.
The opposition MP is not running again.