TUNIS, Tunisia - At least four ministers slammed the door on Tunisia's day-old unity government Tuesday, echoing the concerns of demonstrators who insist democratic change is impossible while so many supporters of the freshly ousted president are hoarding posts of power.

Police in riot gear forcefully put down a demonstration of the sort that toppled the country's longtime autocratic leader last week, pummeling a demonstrator with batons and boot kicks -- and highlighting a question on many minds: Is the new regime really much different?

As Tunisia struggles to move past the rioting, looting and score-settling that has marked the political transition, there was a growing sense Tuesday that it will be difficult for the interim government to hold together and pave the way toward elections expected in six to seven months.

After the initial exhilaration of last week, when a populist uprising ousted President Zine El Abidine Ben Ali after 23 years in power and sent him fleeing to Saudi Arabia -- sounding a warning bell for other political strongmen in the region -- many are fretting about what it ultimately meant.

"I am afraid that our revolution will be stolen from me and my people. The people are asking for freedoms and this new government is not. They are the ones who oppressed the people for 23 years," said Ines Mawdud, a 22-year-old student who was among protesters at the demonstration.

Tunisia's outlawed Ennahdha Islamist party said its members also marched Tuesday -- something that was unthinkable during the rule of Ben Ali, who banned the group in 1992 and waged an ongoing crackdown against it. At the time, authorities accused the group of forming a military wing to kill Ben Ali and establish a Muslim fundamentalist state. Group leaders said their confessions were extracted through torture.

Ben Ali was often criticized for a heavy-handed crackdown on Islamists and opponents, for curbing civil liberties and for running a police state -- though he was praised for turning his country into a successful tourist haven and was an ally in the U.S. fight against terrorism.

In an attempt to distance themselves from Ben Ali, the country's interim president and prime minister on Tuesday quit the ruling RCD party. The RCD party also kicked out Ben Ali, its founder, national television reported. It was not immediately clear how protesters would greet those moves.

Also Tuesday, political leader Moncef Marzouki returned from more than 20 years of exile in France to a joyful reception at Tunis' airport from supporters who carried him on their shoulders.

Marzouki, a physician and human rights activist who leads the once-banned CPR party and wants to run for president, urged fellow Tunisians to hold firm in their efforts to bring down Ben Ali's party.

"Don't let anyone steal this blessed revolution from you," Marzouki said, adding: "Don't waste the blood of our martyrs." That was a reference to the 78 protesters and civilians who died in the month of protests that swept Ben Ali from power. Many were killed by police bullets.

In another blow to the Mediterranean country, whose economy is heavily dependent on tourism, several European tour operators said Tuesday they have cancelled trips to Tunisia through mid-February due to safety concerns.

The new unity government announced Monday was mostly made up of old guard politicians. The four ministers who quit Tuesday had been invited in though they were long critical of the ruling party.

Junior Minister for Transportation and Equipment Anouar Ben Gueddour told The Associated Press on Tuesday that he had resigned along with Houssine Dimassi, the labour minister, and minister without portfolio Abdeljelil Bedoui.

The three ministers are all members of a top labour union, the UGTT. It is not a party but is a movement that acts like a lobby and has a big nationwide base to mobilize people around the country.

The group's supporters staged the protest in central Tunis on Tuesday, calling for a general strike, constitutional changes and the release of all imprisoned union leaders.

Health Minister Mustapha Ben Jaafar of the FDLT opposition party also resigned, party member Hedi Raddaoui told the AP.

Meanwhile, police fired tear gas at protesters angry that the old guard retained so much power.

On a back street off Avenue Bourguiba, a key thoroughfare where the clashes took place, about 50 UGTT members waved union flags and cheered. One sign read "RCD out" in English.

Union leaders said protesters calling for the RCD to be disbanded held peaceful demonstrations in Sidi Bouzid, the city where virulent criticism of Ben Ali's government first erupted last month. Tunisian television said there were protests in at least seven cities.

Mohamed Ghannouchi, who has been prime minister since 1999, maintained that the inclusion of ministers from Ben Ali's party in the new government was needed "because we need them in this phase."

Tunisia has entered "an era of liberty," Ghannouchi said in an interview with France's Europe-1 radio posted on its website. "Give us a chance so that we can put in place this ambitious program of reform."

He insisted the ministers chosen "have clean hands, in addition to great competence," suggesting that experienced officials are needed along with opposition leaders in a caretaker government to guide the country before free elections are held in coming months.

Ghannouchi pledged Monday to free political prisoners and lift restrictions on a leading human rights group, the Tunisian League for the Defence of Human Rights. He said the government would create three state commissions to study political reform, investigate corruption and bribery, and examine abuses during the recent upheaval.

The protests that forced out Ben Ali began last month after an educated but unemployed 26-year-old man set himself on fire when police confiscated the fruit and vegetables he was selling without a permit. The desperate act hit a nerve, sparking copycat suicides and focused anger against the regime into a widespread revolt.

Public protests spread over years of state repression, corruption, and a shortage of jobs for many educated young adults.

Reports of self-immolations surfaced in Egypt, Mauritania and Algeria on Monday, in apparent imitation of the Tunisian events.

The downfall of the 74-year-old Ben Ali, who had taken power in a bloodless coup in 1987, served as a warning to other autocratic leaders in the Arab world. His Mediterranean nation had seemed more stable than many in the region.

British Foreign Minister William Hague warned that it would be wrong to expect events in Tunisia to spark similar protests against other authoritarian regimes in the region.

"It's important to avoid thinking that the circumstances of one country are automatically replicated in another, even neighbouring, country," he told BBC radio, speaking Tuesday during a visit to Australia.