Burning tyres, debris and rocks littered the streets around Independence Square, which police had sealed off to prevent the rally.

Riot police on trucks and foot chased protesters to prevent them from converging there, firing rubber bullets, water cannon and volleys of tear gas throughout the afternoon.

Cat-and-mouse battles continued into the night in the seaside capital, leaving several people including a western photographer and local journalist injured, AFP reporters witnessed.

A policeman was seen firing his gun during a scuffle at the Sandaga market, and an AFP journalist found a spent 9mm bullet casing in the street after protesters lobbed rocks at the police during the ongoing battles.

One police officer fell off a truck after being hit by a rock.

It was the fourth day the opposition had called for mass protests in the capital and a fresh rally has been called for Saturday.

The chaos at the market was sparked by the arrival of music superstar Youssou Ndour.

Ndour has been blocked from running in the election himself but has attended most protests and is fiercely critical of 85-year-old Wade.

Police fired tear gas at least twice at the car carrying Ndour as he was surrounded by fans and dozens of journalists.

When at one point he made as if to get out of his car a police officer in a nearby pick-up shouted at him "Get out of here" as his men launched tear gas.

Police briefly detained opposition presidential candidate Cheikh Bamba Dieye as he attempted to join the protest.

Normally bustling, central Dakar cleared out ahead of the protest Friday afternoon, with shopowners closing up and curious residents and office workers looking on from buildings lining the teargas-filled streets.

One young entrepreneur sold masks to those taking part or witnesses to protect them from the fumes. "I don't care, I am for Wade," he told AFP.

"I just want to make some money. Long live Abdoulaye Wade!"

Tension soared again in the late afternoon when teargas was fired into a mosque in the capital's central Plateau district also near the Sandaga market, prompting fury among those in the area.

Up to 300 people formed a crowd yelling "Allahou Akbar (God is great)", warning police they were pushing the limit.

A religious leader of the Tidiane brotherhood, Serigne Mansour Jamil, accused government of "desecrating Tidiane mosques. By acting this way the whole religious community has been defiled."

"I am saying today, it is time for Wade to go," said Jamil, known as a critic of the president.

The opposition has struggled to get protests off the ground amid government bans and police thwarting their attempts to form a crowd, arresting protesters and dispersing gatherings all week.

M23 coordinator Alioune Tine has denounced the response by riot police to the protests as "completely irrational and dictated by fear".

After calling Friday's protest he said: "On Saturday we will return to the same Independence Square from 11:00 am. It will be a day of action across the whole country."

Tension has soared nine days ahead of the presidential election, dividing a nation that has long enjoyed a reputation as an African democratic success story.

The opposition says Wade has fiddled with the interpretation of the constitution to seek another term.

Wade, Africa's second oldest leader after Zimbabwe's Robert Mugabe, who will be 88 on Tuesday, argues that changes to the constitution in 2008 mean he can serve two more mandates.

Since the official election campaign kicked off Wade has swept energetically through the country promising universities, roads, airports and massive agricultural projects to win over some five million registered voters.

The 13 opposition contenders have failed to find a consensus candidate before the campaign.