The UGTT trade confederation demands a new deal to raise public sector salaries, including retroactively for last year, as the country faces soaring inflation.
Flights have been cancelled, public transport ground to a halt and government offices closed in a nationwide strike by Tunisia's main trade union confederation.
The powerful UGTT confederation had called on up to three million public sector workers to strike on Thursday, halting work at 159 state agencies and public companies to demand concessions on salaries and threatened reforms.
The action appeared to be widely observed in the capital Tunis, where post offices and public utilities were closed.
"This strike is the culmination of a collective failure by more than 10 Tunisian governments, the UGTT, the International Monetary Fund and Tunisia's international partners" to restructure the economy, said Tunisian economist Fadhel Kaboub.
"It will serve as a reminder to the IMF that working people in Tunisia can only sustain so much economic pain."
The strike comes as Tunisia prepares to enter formal talks with the IMF on a new bailout plan for its debt-laden economy.
Soaring inflation, low salaries
While the UGTT's opponents say it is ignoring the country's deep financial woes, its leverage has been boosted by the IMF making a bailout deal conditional on trade union support.
The government has presented a reform plan to the global lender which includes a freeze on the public sector wage bill, progressive cuts to some subsidies and a restructuring of publicly owned companies.
But the UGTT, which has warned against "painful reforms" aimed at pleasing the IMF, has demanded guarantees that state sector firms, including some monopolies, will remain publicly owned.
The UGTT said on Wednesday that its strike action aimed to defend workers' economic and social rights after the "dithering of the government in the face of their legitimate demands".
While the UGTT insists the strike is not political, it comes as President Kais Saied faces intense criticism for excluding opposition forces from his "national dialogue."
The president sacked the government and suspended an elected parliament in July last year, before dissolving the legislature in March and sacking scores of judges by decree earlier this month.
The UGTT was invited to participate in the national dialogue, but refused on the grounds that key political forces were not.
It also argued that the process aimed to push through "conclusions decided unilaterally in advance".