But many opposition groups have condemned the vote as meaningless because some candidates have been barred from participating.
However, the government of President Zine al-Abidine Ben Ali - who has been in power for 18 years - said on Sunday that the vote would strengthen democracy.
More than 10,000 candidates have been vying for 4264 seats on 264 municipal councils across the north African country, which has a population of 10 million.
Analysts predicted the result's will be a foregone conclusion with the ruling Constitutional Democratic Rally party (RCD) winning most of the seats and four legal opposition parties -widely seen as too close to the government- picking up the remaining positions.
Under US pressure
But they said the vote will shed light on the pace of political reform compared with that of countries in the Middle East, where US allies are under pressure to respond to President Bush's drive for more freedom and democracy.
"We wish that the local elections will be another milestone on the path to reinforce the pluralist democratic process," Ben Ali said in a recent speech.
"The municipal elections have no real significance for the political parties and the citizens of this country"
Nejib Chebbi, (opposition)Progressive Democratic Party
The president was re-elected last October with more than 94% of the votes, while the RCD won most of the seats in parliament in simultaneous presidential and legislative polls.
Ben Ali is widely credited with bringing stability and economic prosperity to Tunisia, but rights groups repeatedly criticize his government, accusing it of muzzling the press, jailing dissidents and restricting political life.
Leaders of seven legal but unauthorized political groups said they tried to field about 200 candidates in the name of the Democratic Alliance for Citizenship, but the authorities used threats, bribes or strong-arm tactics to prevent them from standing.
False and baseless
A government source told reporters: "These (opposition) allegations are false and baseless," adding the authorities had rejected the candidate lists of several political parties because they failed to comply with legal conditions.
"The municipal elections have no real significance for the political parties and the citizens of this country," Nejib Chebbi, head of the secular opposition Progressive Democratic Party, told journalists. His party is a member of the Democratic Alliance for Citizenship.
Political analyst Slah Jorchi said there would be no surprises on Sunday. "The citizens, the candidates and politicians know in advance the outcome of the elections. Everything in this vote is decided in advance and to the smallest detail," he said.
Nevertheless Le Renouveau, a publication of the ruling RCD, said in an editorial, "The vote will, without doubt, make the country advance on the path of a pluralist democracy".
President Ben Ali has been trying
to encourage turnout in the elections
One leading political analyst, who declined to be named, said "the elections will shed light on Tunisia as a country that is bucking the reform trend in the Arab world."
Four legal opposition groups -the Movement of Democrat Socialists, the Popular Unity Party, the Union Democratic Party and the Social Liberal Party -are running against the RCD, but most other opposition leaders dismiss them as too close to the government.
Polling booths for the more than 4 million registered voters will have been open today results are expected later on Sunday. Voting is not mandatory but the government has called for a large turnout.