Police have fired teargas to disperse thousands of protesters in the Democratic Republic of Congo's capital.
Demonstrators were angered by Friday's announcement that elections set for later this year could be delayed.
Tensions remain high in the east of the country
Police deployed to prevent thousands of protesters from marching into the centre of Kinshasa. They fired shots in the air and arrested dozens.
A 2002 deal to end five years of war set June as the deadline for elections, while allowing for limited delays.
However, elections chief Apollinaire Malu Malu has indicated the poll will probably take place in October, before heavy rains make parts of the country inaccessible.
Government spokesman Henri Mova Sakanyi played down the protests and said they were organised by supporters of veteran opposition leader Etienne Tshisekedi who has vigorously condemned any possible election delay.
Mr Tshisekedi's UDPS party denied organising the protests but said it understood the anger of the demonstrators.
"The UDPS has not organised demonstrations today but we know there is a lot of discontent amongst the youth and the people on the streets," party secretary general Remy Masamba said.
A five-year civil war in the huge country left nearly three million people dead from hunger and disease.
The war is supposed to have ended in 2002 but fighting has persisted in the east, involving soldiers who were once rebels backed by Rwanda.
Under the peace deal signed by all the main factions at the end of the war, a power-sharing government was tasked with organising elections.
However it does allow for two delays of up to six months each, if approved by parliament.
In a New Year's Eve address, President Joseph Kabila said he was determined to hold the election this year.
"Only credible elections will bring about political stability in our country," he said.
On Thursday, UN chief Kofi Annan said in a report that there were "serious challenges" to holding the election in June.
The UN has also expressed concerns about the logistics of holding an election in a country which is so large yet lacks basic infrastructure, such as roads and railways.
According to the UN's humanitarian chief, Jan Egeland, about 1,000 people are dying every day in DR Congo - many from disease and malnutrition.