A witness reported an explosion on the central Habib Bourguiba avenue where police were cordoning off the area near the capital’s landmark Municipal Theatre.
Nine people, including eight police officers, have been hurt. Their conditions have not been clarified.
The Tunisian Interior Ministry described the attack as a “terrorist explosion”.
Jean-Charles Brisard, president of France’s Centre d’Analyse du Terrorisme, also confirmed the attack.
He said: “A suicide bombing was allegedly perpetrated by a woman who detained her explosive jacket in front of Police Avenue Habib Bourguiba in the centre of Tunis.”
One witness said: “I was in front of the theatre and heard a huge explosion and saw people fleeing.”
Tunisia, which is heavily dependent on tourism, has improved security since a series of militant attacks targeting tourists caused the near collapse of the sector three years ago.
In 2015, 21 people were killed during a hostage siege in its national museum, the Bardo in Tunis, and a gunman killed 38 people on a resort beach.
There have been no attacks on that scale since then, but the economy has remained troubled and the authorities worry about militants who shelter in neighbouring Libya.
Tunisia is one of the few Arab democracies, and the only country to throw off a long-serving autocrat during the Arab Spring popular revolts of 2011 without triggering large scale unrest or civil war.
This is a developing story, more to follow…