Senegal's highest court has ruled that Abdoulaye Wade can run for a third presidential term, sparking angry protests.
Reuters says a TV station in Dakar, the capital, says a police officer has died from head injuries suffered during clashes with protesters.
Witnesses say demonstrators were setting tires on fire and overturning vehicles after the constitutional body announced its verdicts late Friday.
The list of confirmed candidates included the 85-year-old incumbent, but the candidacy of Senegalese pop star Youssou Endure was declared invalid.
After the announcement, police opened fire with tear gas to disperse protesters in central Dakar, who threw who rocks at police and set tires on fire.
Ahead of the court ruling Friday, hundreds of opposition protesters chanted and marched through the streets of Dakar to protest President Wade's plan to can seek a third term.
N'Dour told reporters the constitution makes it clear that President Wade should not have the right to run again.
"History is being made today here in Senegal. We are not going to accept anything else but our constitution, which is very clear. He [Wade] doesn't have the right to run once more. It's my final word on this. It's clear and we are ready,'' said N'Dour.
The Senegalese government initially banned Friday's demonstration, but the country's interior minister said late Thursday the rally would be allowed to proceed.
A Senegalese constitutional amendment limits presidents to just two terms.
Wade was first elected president in 2000, and re-elected in 2007. He argues the amendment does not apply to him since it was not in effect when he first assumed office.
Anti-government riots paralyzed Dakar in June after the ruling party moved to create the post of vice president, and also to lower the percentage of votes needed to win the presidential election.
The president's opponents said the moves were aimed at making it easier forWade to be re-elected, and for his son, Karim Wade, to succeed him. The proposals later were dropped.
Some information for this report was provided by AP, AFP and Reuters.