Several hundred demonstrators tried to march in the city again Thursday, after the lifting of a dusk-to-dawn curfew, but were dispersed when security forces fired tear gas, AFP reporters said.
The overnight clashes broke out in defiance of the curfew with troops deployed into the capital as the authoritarian regime struggled to deal with the worst unrest in the country in more than 20 years.
The Paris-based International Federation for Human Rights (FIDH) branded the government crackdown an "ongoing massacre", adding more than 50 people were wounded in the overnight violence in suburbs of the capital.
"We have a list of the names. We counted 58 deaths since the start of the troubles, outside Tunis. We have just received confirmation of eight deaths and 50 wounded in the night in greater Tunis," President Souhayr Belhassen said.
"The priority of priorities today is to stop this massacre," she said.
The United Nations, European Union and United States have also expressed concern about the government's crackdown.
The dead included a university lecturer with joint French and Tunisian nationality and a Swiss-Tunisian, it was announced Thursday.
In a statement confirming the death of its national, the Swiss foreign ministry called on "Tunisia to respect dialogue, fundamental liberties and human rights -- these include the freedom of opinion and assembly."
Among the latest fatalities were two men shot dead by police as they were heading for home before the curfew in the city's Ettadhamen suburb Wednesday, a witness and an AFP journalist said.
They were named as Magid Nasri, 25, and Malek Habbachi, 24.
Another witness told AFP that a 19-year-old man had died after being shot by police late Wednesday in the town of Sfax, 300 kilometres (180 miles) southeast of the capital.
Clashes also broke out Wednesday in the central town of Douz and Thala in the west, with three people reported killed and several wounded altogether.
There has been no government confirmation of the latest deaths.
The interior ministry has acknowledged 21 deaths in the worst unrest which raged over three days last weekend in the western Kasserine region, but said security forces acted in self defence. A union said more than 50 were killed.
The violence flared after weeks of protests that initially focused on unemployment, sparked by the suicide of a young graduate who set himself a light on December 17.
Struggling to contain the unrest, the government of President Zine El Abidine Ben Ali on Wednesday sacked its interior minister, in charge of police, and pledged to investigate claims of excessive use of force.
Ben Ali also promised to create 300,000 more jobs and called a conference on employment for next month.
But the opposition has said the measures fell far short of the "deep reforms" required.
"Tunisia needs global reform as well as the formation of a national unity government more than ever," Progressive Democratic Party (PDP) secretary general Maya Jribi said in a statement.
Jribi called for a constitutional amendment "to guarantee a peaceful handover of power" and reestablish security "so as to avoid chaos".
UN High Commissioner for Human Rights Navi Pillay on Wednesday called for the government to "launch a transparent, credible and independent investigation into the violence and killings".
Members of the security forces should be punished if found guilty of excesses, she said.
Police meanwhile detained a Communist party leader, his wife said, making him the first politician arrested since the unrest began.
Hamma Hammami, the leader of the Tunisian Workers' Communist Party (POCT) which is banned by the government, has repeatedly denounced Ben Ali's government to foreign media.