Presidential candidates have been participating in the campaign against a third term for President Wade [EPA]

Senegalese police have violently dispersed opposition protesters demonstrating in the capital, Dakar, in the run-up to a crucial presidential election.

Several hundred people turned out on Wednesday in defiance of a government ban and attempted to reach the presidential palace before being blocked by a column of soldiers.

Riot police fired tear gas and used used truncheons as well as a water cannon to disperse the protesters as they attempted to assemble for a banned march against President Abdoulaye Wade's third-term candidacy in the February 26 polls.

Police pushed back groups of opposition protesters who attempted to converge in the suburb of Medina, later firing tear gas as they tried to begin the march to Independence Square in the heart of the city.

At the square itself, another candidate Bamba Dieye rallied a small crowd of people, which grew to several hundred as riot police blocked the road to the presidency.

Someone had spray-painted "Wade Degage" (Get Out Wade) and other graffiti on the street circling the square. Police fired volleys of tear gas and sprayed protesters with water as they dispersed and later regrouped.

Perched on the roof of a 4X4, Dieye and Fall denounced "the violation of their constitutional rights".

As calm and traffic returned to the square, music superstar Youssou N’Dour made an appearance.

Senegal's most famous export, N’Dour has remained at the head of the anti-Wade campaign even after his own candidacy was blocked by the constitutional council, the country's top court.

"Senegal needs to free itself, to rediscover its democracy ... We are allowing a dictatorship to set in here," he said as dozens of fans clamoured around holding up cellphones and cameras.

Wade, Africa's second oldest leader after Zimbabwe's Robert Mugabe, argues that changes to the constitution in 2008 mean he can serve two more mandates.

Government's warning

Senegal's interior minister had said that the government has the right to "restrict such liberties through legal channels when there is a real threat to public order".

Ousmane Ngom told the opposition in a statement sent before the planned march: "I inform you that the demonstrations you plan cannot happen at the foreseen date and place."

In the message to leaders of the June 23 Movement [M23] the minister warned: "The administration will take all its responsibilities to ensure the safety of people and property."

Before the ban was announced, Alioune Tine, an M23 co-ordinator, declared: "We are going to hold our march tomorrow, nobody can stop us. We condemn the Senegalese administration's biased attitude. At this rate, it will end up being responsible for violence."

Violent protests erupted in Dakar and spread through the country, leaving four people dead, on January 27, when the country's highest court validated Wade's candidacy for a third term which the opposition says is unconstitutional.

M23, which includes several presidential candidates, have pledged unity in pressuring Wade to step aside. However, their campaign of resistance has appeared to lose steam in recent days.