Tunisia is experiencing a nationwide strike after protests over the killing of opposition leader Mohamed Brahmi.
The biggest trade union, UGTT, called the shutdown to denounce general “terrorism, violence and murders”.
On Thursday police used tear gas to disperse protesters in several towns, after Mr Brahmi was shot dead outside his home in Tunis.
The governing Islamist Ennahda party has rejected accusations from relatives that it was complicit in the killing.
Unidentified gunmen on a motorbike shot Mr Brahmi – who led the Movement of the People party – in his car on Thursday morning
He is the second politician to be killed so far this year. In February, the murder of prominent secular figure Chokri Belaid sparked mass protests and forced then-Prime Minister Hamadi Jebali to resign.
Although not as prominent as Mr Belaid, Mr Brahmi too was a leftist critical of Ennahda, which came to power after the overthrow of long-term ruler Zine al-Abidine Ben Ali in January 2011.
After the UGTT issued its strike call, on Thursday protesters gathered in cities across the country to call for the government to resign. Police fired tear gas during disturbances that continued overnight.
Demonstrators attacked Ennahda’s headquarters in Sidi Bouzid, Mr Brahmi’s hometown and the birthplace of the Arab Spring revolutions, which have swept the Middle East.
One protester in the town told Reuters news agency: “They (Ennahda) gave the green light to kill Tunisian people. We used to support them. But now, they want to get rid of us.”
The UGTT called for a two-hour strike on Friday. All Tunisair flights to and from the country have been cancelled throughout the day.
The family of Mr Brahmi has accused Ennahda of being behind the killing.
The party’s chief – Prime Minister Rached Ghannouchi – rejected the charge, calling Brahmi’s killing “a catastrophe for Tunisia.”
In an interview with AFP news agency, he said: “Those behind this crime want to lead the country towards civil war and to disrupt the democratic transition.”
Meanwhile President Moncef Marzouki told France’s Le Monde newspaper he had “no doubt” that Mr Belaid and Mr Brahmi had been assassinated by the same people, and that the killers’ aim was to destabilise Tunisia.
There has been deep division in the country between Islamists and secular opponents since Ennahda came to power.
The party has faced growing popular unrest over a faltering economy and a rising extremist Islamist movement.
Correspondents say many Tunisians, particularly the young, complain that their quest for secular democracy has been hijacked by intolerant Islamists, including the Muslim Brotherhood which forms part of the current government.