Police in Democratic Republic of Congo's mining hub fired tear gas on Tuesday at opposition supporters brandishing sticks and shovels who were protesting against arrests targeting youth leaders.
Political unrest has spread across the country, Africa's top copper producer, as opposition parties accuse President Joseph Kabila of seeking to circumvent a constitutional term limit and hang onto power beyond the end of his current mandate next year.
Gabriel Kyungu wa Kumwamza, president of the National Union of Federalists of Congo (UNAFEC), said soldiers arrested about 15 youth members early on Tuesday at the party's headquarters in Lubumbashi, the main city in the copper-rich Katanga region.
"It is simply provocation and harassment," he said. "The people in power know that they are going to fail. That is why they don't want there to be elections. They want to provoke problems so that the elections don't happen."
UNAFEC is one of several parties that were expelled from the ruling coalition in September after they demanded immediate steps to ensure that a presidential election scheduled for November 2016 is held on time.
A local police commander said problems initially arose early on Tuesday as a result of UNAFEC youth members who he claimed were hassling people at one of the city's public markets.
Later, several hundred UNAFEC supporters shouted abuse at dozens of police officers massed near the party's headquarters before some began throwing stones at the security forces, who responded with volleys of tear gas.
Several African governments, including Rwanda and Democratic Republic of Congo's smaller neighbor Congo Republic, have changed their constitutions or are taking steps to do so in order to prolong long-ruling presidents' time in power.
Kabila's spokesman has repeatedly stated that he plans to respect the constitution and on Monday he called for a national dialogue on the organization of the elections.
"The President of the Republic promises to put in place a preparation committee to determine the format and the issues to be treated," Senate president Leon Kengo wa Dondo told the body.
A number of opposition figures have already rejected the proposed talks, however, claiming it is part of a strategy to delay the polls.
"The dialogue called for by Joseph Kabila is pointless. All the government has to do is respect the legal and constitutional texts for everything to happen calmly," said Valentin Mubake, an influential member of the opposition Union for Democracy and Social Progress.