TUNIS: Tunisia's government on Tuesday dismissed five senior officials, including the interior ministry's top security chief, a week after a suicide bombing killed 12 presidential guards in an attack in the centre of the capital.

Tunisia, mostly a haven of stability since its 2011 revolt against autocrat Zine Abidine Ben Ali, is increasingly being challenged by Islamist militants and authorities have kept a state of emergency in place since the Nov. 24 attack.

The prime minister's office said that the secretary of state for security "has been relieved of his post" and the interior ministry said four other senior officials were dismissed. Neither the prime minister's office nor the interior ministry gave any details of the reasons for the dismissals.

Authorities on Tuesday said they had seized a cache of arms and explosives, the second such operation in two days.

The bus bombing in Tunis was the third major militant attack in Tunisia this year and responsibility was claimed by Islamic State, the group that controls parts of Iraq and Syria and has supporters elsewhere in the world. The two other attacks targeted foreign visitors - one on a beach resort at Sousse and the other at the Bardo museum in the capital.

Several thousand Tunisians are fighting with Islamic State and other groups in Iraq and Syria. The gunmen in the Sousse and Bardo Museum attacks all trained at militant camps in Libya.