People in Benin are voting for a new parliament but without a single opposition candidate taking part.
The electoral authorities ruled last month that only two parties - both loyal to President Patrice Talon - met the requirements to take part.
New electoral laws mean a party had to pay about $424,000 (£328,000) to field a list for the 83-seat parliament.
Internet access has been restricted with social media and messaging apps blocked in the West African nation.
Five million people are registered to vote in the country, known as one of Africa's most stable democracies.
Rights activists have criticised a ban and crackdown on peaceful protests by those angered by the opposition's exclusion as well as the arrests of political activists and journalists.
"The growing wave of arrests and detentions in Benin is extremely troubling, particularly in the context of elections," François Patuel, from UK-based Amnesty International, said in a statement.
"Banning peaceful protests and detaining those who speak up against the exclusion of opposition parties from the legislative election will only fuel political turmoil."
Last week, security forces fired tear gas as two former presidents - Nicéphore Soglo and Thomas Boni Yayi - addressed an impromptu demonstration about the elections in the main city of Cotonou.
Five years ago voters in Benin, which introduced multi-party elections in the 1990s, could chose from 20 parties for the 83 seats in parliament, AFP news agency reports.
President Talon, a former businessman known as the "king of cotton", came to office in 2016 on a modernist ticket.
He says the electoral reforms were intended to bring together the country's several hundred political parties into streamlined blocs.
He has also overseen laws barring health workers from striking and limiting strikes by other civil servants or government workers to 10 days a year.
Correspondents say many people had expected him to postpone the vote to give the opposition time to meet the new requirements.
But in a national address on 11 April, President Talon said that he did not have the power to interfere in the electoral process.
On Sunday morning, voter turnout was slow in Cotonou, AFP says.