The suspected mastermind behind the deadly March 18 attack on Tunisia's Bardo National Museum has been killed, Tunisian officials said Sunday.

Tunisian Prime Minister Habib Essid announced that Khaled Chaieb, also known as Lokman Abou Sakhr, was killed in a dawn raid by the country's national guard, according to state-run press agency TAP. Chaieb was the suspected leader of an al Qaeda branch called the Okba Ibn Nafaa Brigade.

Essid said the raid occurred in the Gafsa region in southwest Tunisia. He called it just the "first reaction" to the terrorist attack in Tunis that initially left 21 people dead, including two gunmen. A French woman injured in the attack died on Saturday, bringing the total number of dead to 22.

"The Gafsa operation was crowned with great success," Essid said, according to TAP. "It is a delicate operation implemented for the first time since the start of the fight against terrorism."

Interior Ministry spokesman Mohamed Ali Laroui said a total of nine suspects were killed in the raid early Sunday morning.

Laroui said Thursday that Tunisian authorities had arrested "80 percent" of the terrorist cell suspected of planning the Bardo attack. The Islamic State previously claimed responsibility for the attack, but Laroui blamed al Qaeda's offshoot in North Africa.

"For the purpose of propaganda, publicity, the Islamic State praised this act," Laroui told AFP earlier this week. "But on the ground, it was Okba Ibn Nafaa, which belongs to al Qaeda in the Islamic Maghreb (AQIM), who planned and carried out this crime."

The terrorist attack has shaken a country that has been held up as a success story for transitioning to democracy without widespread violence following the Arab Spring protests. Thousands of Tunisians and several foreign leaders took to the streets Sunday to protest the attack and stand in solidarity against terrorism.

French President Francois Hollande and Italian Prime Minister Matteo Renzi traveled to Tunis to take part in the demonstration. Many of those killed in the museum attack were foreign tourists from Italy and France.

Along with the foreign leaders, thousands of Tunsians marched under banners and waved flags. One banner held by protesters read, "Le Monde est Bardo," or "The World is Bardo."

The Bardo National Museum is scheduled to reopen Sunday to the public for the first time since the March 18 attack.