A policeman was reportedly killed as protests swept across Senegal after a court cleared President Abdoulaye Wade's bid for a third term.
Angry youths spread through the streets of Dakar, burning tyres and brandishing rocks as a mass gathering turned violent in the capital.
Discussing the clashes between police and demonstrators in the capital, Dakar police commissioner Arona Sy told reporters the protesters "killed a policeman" - without saying how he died.
Police officers were seen using teargas in retaliation to protesters hurling stones.
Rivals to 85-year-old Mr Wade say the constitution sets an upper limit of two terms on the president.
But the leader, who came to power in 2000 and was re-elected in 2007, has argued his first term pre-dated the 2001 amendment establishing the limit.
Senegal's Constitutional Council - the country's top court - validated his candidacy and that of 13 rivals for the vote on February 26.
But it turned down the presidential bid of one of Africa's biggest music stars, Youssou N'Dour , saying he had not gathered the required 10,000 signatures of support.
Mr N'Dour called on his supporters to prevent the elections from going ahead.
"We will never allow Abdoulaye Wade to take part in the election," he said, speaking on his own TFM television channel.
The June 23 Movement (M23) of opposition against Wade's candidacy, which called Friday's rally, appealed to Senegalese to march on the presidential palace in downtown Dakar.
Spokesman Abdoul Aziz Diop said the M23 "calls on the Senegalese people to mobilise and march on the Presidential Palace and remove Wade, who is squatting there."
Senegal is the only country in mainland West Africa to have not had a coup since the end of the colonial era.
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