Protesters clashed with Senegalese police in Dakar on Tuesday after demonstrating against a decision by President Abdoulaye Wade to seek re-election.
The protesters threw rocks at the security services who responded with tear gas and batons.
One woman was reported to have been injured.
They are angry about a constitutional Court ruling allowing 85-year-old Wade to run for a third term in the February 26th presidential election.
The opposition disputes his claim that 2008 constitutional change allows him to stay on.
Wade has been in power in Senegal since 2000.
Musician Youssou N’Dour had wanted to stand, but the court barred him from doing so on the grounds he lacked the required 10,000 signatures of support.