Protesters on Monday hurled rocks at Tunisia's President Moncef Marzouki and parliamentary speaker Mustapha Ben Jaafar in Sidi Bouzid, cradle of the revolution that erupted exactly two years ago.
The incident began after a speech by Marzouki and as Ben Jaafar was about to address the crowd in the poor Tunisian town, where muted celebrations are taking place to mark the anniversary of the uprising.
Tunisia's marginalised interior has witnessed frequent outbreaks of social unrest amid bitter frustration at the revolution's failure to bring material benefits.
The security forces swiftly evacuated the two men to the prefecture, or regional government headquarters, an AFP journalist reported.
The protesters invaded the square where the speeches were taking place, shouting "the people want the fall of the government."
The police held back, after violent clashes in Tunisia in recent few months, often following attempts by the security forces to disperse protesters angry over the government's failure to improve living conditions.
When the president took to the podium on Monday, many in the crowd of around 5,000 started shouting "Get out! Get out!" -- one of the rallying cries of the revolution that toppled the regime of former dictator Zine El Abidine Ben Ali.
Marzouki had promised economic progress within six months, after meeting residents of Sidi Bouzid, who complained about the lack of infrastructure.
Poverty and unemployment were key factors behind the mass protests that erupted after a 27-year-old street vendor set himself on fire outside the governor's office on December 17, 2010, to protest against police harassment.
Ongoing insecurity and the crisis in Europe have hampered Tunisia's economic recovery, after last year's recession, and unemployment, pegged at around 18 percent, is especially high among young Tunisians, fuelling their anger and frustration.
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Last month, around 300 people were wounded in five straight days of clashes between police and protesters in the town of Siliana, southwest of Tunis, where a strike swiftly degenerated into violence.
The president, a secular, centre-left ally of the Islamist party Ennahda, which heads Tunisia's ruling coalition, stressed that the government did not have a "magic wand" to fix the country's problems, and urged patience.
"The government does not have a magic wand to change things... It will take time to mend what we have inherited from 50 years of dictatorship," said Marzouki, who was jeered by the crowd.
Marzouki had been heckled earlier in the morning, when he laid a wreath of flowers at the grave of Mohamed Bouazizi, the young fruit and vegetable seller whose act of desperation touched off the Arab Spring.
"The people in government act like they're punishing us for starting the revolution. Nothing has changed for us," said Midani Khassemi, an unemployed 36-year-old, who was wounded in last year's uprising.
The Islamist-led government has struggled to meet the expectations of many ordinary Tunisians, with clashes and strikes, as well as attacks by Islamists, multiplying across the country in the run-up to Monday's commemorations.
Radical Islamists also gathered outside the prefecture in Sidi Bouzid on Monday, with members of the Hizb Ettahrir party waving the black flag of the hardline Salafist movement.
The Salafists have been implicated in numerous acts of violence since the revolution, including against Sufi shrines and art galleries and an attack in September on the US embassy in Tunis that left four people dead.
Reflecting heightened political tensions, Tunisia's main labour union, the UGTT, had planned to hold a nationwide general strike last week in protest at an attack on its offices by activists allied to Ennahda. It cancelled the strike at the last minute, after reaching a deal with the government.
The country has also been plunged into an impasse over the drafting of a new constitution, which has been delayed by disagreement among lawmakers over whether the political system should be presidential or parliamentary.