Tunisia, the country whose protest movement promised to transform the Middle East a decade ago, is in turmoil after its president suspended parliament and seized executive power this week, stirring concerns that the only democracy to emerge from the Arab Spring uprisings is slipping back to autocracy.

The crisis is threatening to strike a blow against democratic aspirations across the region, and while many Tunisians support the removal of an unpopular government, others fear the country could lose its status as North Africa’s sole exemplar of democracy after street rallies overthrew a dictator in 2011. Egypt’s brief period of democracy ended in a military coup in 2013. Libya, Syria, and Yemen plunged into war.

“It means that we are not different, maybe,” said Messaoud Romdhani, a Tunisian activist and political analyst who sits on the board of Euromed Rights, a regional network of human rights groups. “It means the only success story has come back to the group.”

President Kais Saied fired top government ministers and sent troops to stop lawmakers from entering the parliament building Monday, after months of antigovernment protests over a faltering economy and a Covid-19 outbreak that pushed hospitals to the brink. On Monday, he imposed a ban on gatherings of three or more people that largely halted protests.

Soldiers guarded parliament’s main entrance as demonstrators gathered outside Monday.

Soldiers guarded parliament’s main entrance as demonstrators gathered outside Monday.

Photo: Hedi Azouz/Associated Press

Top political leaders, including the speaker of the parliament, Rached Ghannouchi, have accused Mr. Saied of launching a coup. Mr. Saied has rejected that, saying the constitution gives him emergency powers. Mr. Ghannouchi has said he wasn’t consulted on the moves, which would render them unconstitutional. Tunisia currently has no constitutional court to rule on the dispute.

Tunisian officials said Wednesday that prosecutors had launched an investigation into Mr. Ghannouchi’s Islamist Ennahdha party, plus two other parties, regarding allegations of receiving foreign funds for campaigning, adding to fears of a further crackdown. The parties didn’t immediately comment on the charges.

The crisis has been years in the making. Behind Tunisia’s reputation as the region’s democratic showcase was an incomplete revolution, many Tunisians say. After the fall of autocrat Zine El Abidine Ben Ali in January 2011, police and security forces from the old regime resisted attempts at reform and accountability. Wealth remained concentrated among a handful of well-connected families.

Political deadlock made matters worse. Tunisia’s political system divides power between the president and a prime minister selected by the parliament, who runs the government. This left the country without a coherent plan to build the economy and tackle problems such as the coronavirus pandemic. Tunisia agreed to a series of loans via an International Monetary Fund program that led to budget cuts and ultimately, higher taxes on gasoline, phone cards and fruit and vegetables. The toll on ordinary Tunisians was worsened by authorities’ failure to uproot endemic corruption.

The result was that Tunisians had won freedom of expression and elected governments, but lacked jobs and services. The perceived lack of opportunities drove thousands of Tunisians to leave, including via smugglers’ boats to Europe. Despair drove others to suicide. Cases of self-immolation, a form of protest popularized in the 2010-2011 uprising, tripled during the five years after the revolution, according to a study published in the British Medical Journal, with 148 instances occurring between 2011 and 2015.

“It’s all about power and incompetence. They [the government] don’t have a strategy and a vision for the economy except renegotiating loan terms with the IMF and overtaxing businesses,” said Samy Ashour, owner of a Tunisian technology business.

Public dissatisfaction boiled over in recent months, as the long-neglected healthcare system buckled under the pandemic. Tunisia has suffered one of the highest per capita death rates in the world in recent weeks, driven in part by the spread of the Delta variant. Tunisia has registered 167,985 new cases and 4,314 new deaths over the last month.

Tunisia’s Covid vaccine rollout became another example of the political dysfunction. After the government started offering inoculations to all Tunisians over age 18 in July, stampedes took place at vaccination centers. Prime Minister Hichem Mechichi fired the health minister. The president blamed Mr. Mechichi and the Islamists in parliament for the chaos.

Furious, protesters surged into the streets again Sunday, demanding the fall of the government.

“It was a reaction over 10 years of marginalization, poverty, terrorism, and political assassinations under successive governments led by the Ennahdha party,” said Intissar Gassara, a 28-year-old activist and law student in Tunis.

Kais Saied was sworn in as president on Oct. 23, 2019.

Kais Saied was sworn in as president on Oct. 23, 2019.

Photo: Khaled Nasraoui/Zuma Press

Mr. Saied, an independent who had never held office before winning the presidency, is betting the public will blame political parties, parliament and the deposed government for Tunisia’s woes, analysts say. Early indications suggest some Tunisians now want him to go further and overhaul the wider political system.

“We wanted him to take more brave actions instead of just freezing the parliament,” said Zouhair Lajmi, a 62-year-old activist from the city of Sfax, who wants the authorities to prosecute alleged corruption.

The aftershocks appear far from over. Mr. Saied hasn’t specified a path forward and he faces opposition from the four largest parties in parliament, civil-society groups and others.

“We’re still in the middle of a fight. We are not finished,” said analyst Mr. Romdhani.

—Ghaya Ben Mbarek in Tunis, Tunisia, contributed to this article.

Write to Jared Malsin at jared.malsin@wsj.com