* Street clashes continue in centre of capital
* EU flags concern over ban on demonstrations
* Obasanjo says to observe, but ready to intervene
By Joe Penney and Diadie Ba
DAKAR, Feb 21 (Reuters) - Hundreds of opposition supporters clashed with Senegalese security forces in the capital on Tuesday as European Union observers criticised a ban on protests and an African envoy jetted in to try and stem rising violence.
A Reuters witness said police fired teargas and demonstrators hurled rocks in central Dakar, where opposition supporters have tried to protest in the main square against President Abdoulaye Wade’s candidacy in an election on Sunday.
Tuesday’s clashes underscored mounting tensions in the West African state, which has enjoyed decades of democracy but is gripped by a row over whether Wade should be allowed to run for a third term in power.
Six people have been killed in election-related violence so far. Opposition supporters have increasingly sought to defy bans on protests by the authorities, leading to cat-and-mouse street battles in the capital and other towns.
The EU election observer mission expressed “its concern over the Interior Ministry’s ban on demonstrations”, a statement said. It added that Senegalese law allowed for such demonstrations when they involve presidential candidates.
The EU mission called on all sides to refrain from violence but it also repeated an appeal for the government to provide more transparency over the distribution of election cards.
Some 600,000 newly registered voters from an electorate of just over 5 million must collect their election cards and the EU mission warned last week that many had not done that yet, potentially ruling them out from voting.
Wade’s rivals said his candidacy is illegal because it breaches rules setting a two-term limit, and accused the octogenarian leader of backtracking on his own statements that he would not be able to stand for re-election.
The president has argued that he is eligible to stand as the limits were added to the constitution after he had started his first term in 2000.
The United States, a key donor of Senegal’s, has warned that Wade’s candidacy risked destabilising a nation long seen as a bastion of democracy in a troubled region. Former colonial power France has said it would like to see power transferred to a younger generation.
Wade’s camp has said it was up to the Senegalese to decide who ran the country.
Olusegun Obasanjo, the former president of Nigeria, arrived in Dakar on Tuesday having been dispatched by both the West African regional bloc ECOWAS to promote dialogue between the parties and the AU to monitor the elections.
Asked to clarify the twin role, Obasanjo told reporters that he had been tasked with observing the election but he would also be ready to intervene in case the situation on the ground required it. He did not elaborate.
Some minor candidates have called for Sunday’s vote to be delayed but most, including the leading opposition figures, have not, even though they say they will not recognise Wade’s candidacy.
“Unfortunately, the only thing that will get people to sit down to talk is a certain level of violence,” a diplomat monitoring the process told Reuters. (Additional reporting and writing by David Lewis; Editing by Alessandra Rizzo)