Opposition activists in the Togo capital, Lome, have clashed with police after setting up road blocks made from burning tyres.
Several opposition protests have been held in Lome
The police fired tear gas at the protesters, preventing some 2,000 people from marching into the city centre from their suburban strongholds.
The clashes came on the first day of campaigning for the 24 April polls, which the opposition want postponed.
The elections follow February's death of President Gnassingbe Eyadema.
His son, Faure Gnassingbe, was originally installed in office by the Togolese army, but he later bowed to international pressure and stepped down, agreeing to contest an election.
The opposition say they have not been given enough time to mount a proper campaign.
They also say that the distribution of voters cards has favoured ruling party strongholds.
On Thursday, Interior Minister Francois Boko announced that eligible voters in Lome would be able to get their cards at two football stadiums at the weekend, even though the process officially ended earlier this week.
Police and opposition activists also clashed on Wednesday.
Ruling party supporters say any delay in the poll would be a danger for the country.
Emmanuel Bob-Akitani, Vice-President of the Union of Forces for Change party, will stand as the main opposition candidate against Faure Gnassingbe.