The French president's office says that a fourth French citizen, seriously injured in the March 18 attack on Tunisia's National Bardo Museum, has died, bringing the total number of victims to 22.

The announcement on Saturday identified the woman only as Madame Dupeu.

Police killed two gunmen in the attack in the most renowned museum in the North African country.

News of the death came a day before President Francois Hollande joins other leaders for a Sunday march in Tunisia's capital, Tunis. Thousands of Tunisians were expected to take part.

The Islamic State group claimed responsibility for the attack. Authorities have made arrests but are hunting for the suspected mastermind. Five security officials were fired after the attack. A police officer responsible for museum surveillance was jailed.