A wanted militant wearing an explosive belt blew himself up in the Tunisian capital after being surrounded by police, the government said on Wednesday, but there were no other casualties.
The third such incident within a week comes months ahead of an election and at the peak of a tourist season in which Tunisia is hoping for a record number of visitors.
Earlier, witnesses said that a man blew himself up in the Mnihla area in Tunis after being surrounded by the police.
The spokesman said police opened fire on the man, whom authorities described as a wanted militant called Aymen Smiri.
He was the suspected mastermind of last week's twin suicide bombings and he was killed in an overnight firefight with police outside the capital, the interior ministry said on Wednesday.
"The terrorist Aymen Smiri was implicated in the twin suicide bombings on Thursday and investigations proved that he was the mastermind of the operation," interior ministry spokesman Sofiene Zaag said, adding he was a "very active and very dangerous leader."
Two suicide bombers blew themselves up in separate attacks on police in Tunis on Thursday, killing one police officer and wounding several other people. ISIS claimed responsibility for the two attacks.
Tunisia has been battling militant groups operating in remote areas near the border with Algeria since an uprising overthrew autocratic leader Zine Abidine Ben Ali in 2011. High unemployment has also stoked unrest in recent years.
Last October, a woman blew herself up in the centre of Tunis, wounding 15 people including 10 police officers in an explosion that broke a long period of calm after dozens had died in militant attacks in 2015.
Security has tightened since authorities imposed a state of emergency in November 2015 after those attacks, one at a museum in Tunis and another on a beach in the Mediterranean seaside town of Sousse. A third attack targeted presidential guards in the capital. ISIS claimed responsibility.
