An unemployed man has set himself on fire in the centre of Tunis in a gesture recalling the self-immolation of Mohamed Bouazizi, whose death ignited a revolt in Tunisia that echoed across the Arab world.
Security forces and bystanders tried to extinguish the flames before the man was rushed to hospital, witnesses said.
"He is in very critical condition," a medical source in Mourouj hospital said, but gave no further details.
The incident occurred hours before the prime minister designate, Ali Larayedh, was due to seek a confidence vote for his new Islamist-led government from the National Constituent Assembly.
The man burned himself outside the municipal theatre in the capital's main Habib Bourguiba Avenue, the focus for protests that toppled the former president Zine al-Abidine Ben Ali two years ago.
An interior ministry official did not name the victim, but said he was 27, came from the north-western city of Jandouba and had been out of work for some time.
Tunisia's unemployment rate stands at about 17%, with graduates forming a large proportion of the jobless total.
Several Tunisians have set themselves ablaze in the past two years in protests emulating that of Bouazizi, a street vendor who torched himself on 17 December 2010 in the town of Sidi Bouzid after a policewoman confiscated his fruit cart.
The economic and social problems that fuelled Tunisia's uprising have yet to be solved in a country deeply polarised between Islamists and their opponents and still awaiting a new constitution to advance a transition from autocracy.
The last government, led by Hamadi Jebali, collapsed after the premier's own moderate Islamist Ennahda party rejected his plan for a technocrat cabinet to lead Tunisia to elections.
Jebali had proposed this as a way to calm unrest over the assassination on 6 February of the secular opposition leader Chokri Belaid by what the authorities say was a group of Salafi Islamist militants, four of whom have been arrested.
Larayedh, who was interior minister under Jebali, has asked independents to take several key portfolios, but failed to bring additional secular parties into the Ennahda-led coalition.
The political crisis has delayed talks with the International Monetary Fund on a $1.78bn loan.