Details added (the first news was posted at 19:05)
Tunisian Prime Minister Mohammed Ghannouchi announced his resignation on Sunday, reported Al-Arabiya TV station.
"I have decided to quit as prime minister," Ghannouchi told a news conference, adding "This resignation will serve Tunisia, and the revolution and the future of Tunisia."
He stressed the necessity and importance of establishment of a new constitution, base on which the country could move forward, Xinhua reported.
Ghannouchi has long been accused by protestors as "being too close" to the toppled regime of Ben Ali.
Three people were killed and nine others injured in clashes between protesters and the police in central Tunis on Saturday, the official TAP press agency reported.
More than 3,000 demonstrators gathered on Feb. 20 on Kasbah square, calling for the resignation of Mohammed Ghannouchi and the establishment of a parliamentary system in the country.