A tourist is helped to a vehicle after an attack by gunmen on Tunisia's national museum in Tunis on March 18, 2015. Reuters

Tunisian authorities have arrested four relatives of an assailant killed during the Wednesday attack on the National Bardo Museum in Tunisia’s capital, Agence France-Presse reported Friday, citing family and police sources. Two brothers, a sister and father of the Khachnaoui family were arrested Wednesday near the border with Algeria.

The relatives were taken into custody Wednesday night in Kasserine, where the family owns a small farm. Tunisian Prime Minister Habib Essid earlier Wednesday had identified one of the two attackers killed in the museum massacre as Hatem Khachnaoui. But police in Khachnaoui’s home of Ibrahim Zahar, a village in Tunisia's West Central province, said his first name was Jabeur, according to AFP.

Tunisian authorities arrested a total of nine people Thursday in connection with the attack, during which five gunmen stormed the National Bardo Museum in Tunis. Twenty-three people were killed in the raid, mostly foreign tourists. Khachnaoui and a second attacker, identified as Yassine Laabidi, were killed by security forces at the scene and counted among the 23 dead.

The attack came just two days after social media accounts associated with the Islamic State group claimed that a planned attack on Tunisia was imminent. The terror group claimed responsibility for the assault Thursday.