Fabiani warned, however, that Ennahda, which he called "the most moderate Islamic party in the Arab world," might radicalize if it is pushed out of power and does poorly in upcoming elections.
"Ennahda has moderated, but if they're out of government the hardliners of the party could play a different game," he said. "This could stir up increased tension on the street and lead to more violence."
Since its election, Ennahda has worked with other secular parties and compromised with the opposition on issues such as not enshrining Islamic law in the constitution currently being written. Now, however, there are growing signs of divisions within the party and fears that the hardline elements might be backing the groups carrying out violence.
"We're at an impasse," said Moncef Nasri, a Tunis writer and journalist. "All parties have to cooperate to create a clear path out of this very serious situation." But he said he is confident that Tunisia will pull back from the brink, as it has done repeatedly in the years since its so-called Jasmine Revolution.
"It's because of our history, our cosmopolitan culture," Nasri said. "Tunisia has always welcomed people from all faiths and cultures."
After three days of street violence, the capital Tunis was relatively quiet Sunday, under the watchful eye of riot police.
The assassination of Belaid unleashed pockets of pillaging and unrest on Saturday, including an attack by 80 youths armed with stones and clubs on a police station and a second security post in Zaghouan, 25 miles (40 kilometers) west of Tunis, the official TAP news agency reported. To the south, in the town of Kebili, 60 people, mainly youths, attacked the governing Ennahda party offices. The extent of that damage was not immediately known.
Associated Press reporters Oleg Cetinic and Bouazza ben Bouazza in Tunis contributed to this report.