Ayman Muhammad Habib, his deputy, will replace him, the local Arabic daily announced Friday.
The paper gave no reason for the reshuffle but said Al-Tunisi resigned for personal reason.
Local newspapers, however, said Al-Tunisi resigned after differences with the management of Okaz Organization for Press and Publications that had been ongoing for more than six months.
They claimed he would not deny or confirm these reports but quoted him as saying that he had submitted a resignation letter outlining his reasons.
Al-Hayat newspaper quoted Al-Tunisi as saying that he was ready to serve his country in any position, but that he would not accept oppression against editors.
The newspaper said Al-Tunisi declined to elaborate on the alleged oppression he had suffered, but he also reportedly said: "This is the first time I am resigning, but the last time as well."
He confirmed that he would not go back on his decision but said it was premature to speak about his future at this time. "I have not yet enjoyed my resignation," he reportedly said.
On the other hand, local daily Al-Watan quoted Al-Tunisi as saying that he would offer his experience in the literary, visual and electronic media to honor his national commitments.
He also refused to answer a question on why he resigned but said his letter of resignation contained the reasons.
"When I leave a place I turn my back to it but keep the beautiful things to myself," he added, recalling that he issued 900 editions of the newspaper.
Al-Tunisi told Al-Watan that his resignation was accepted after editorial posts in Al-Jazeerah, London-based Asharq Al-Awsat, Al-Eqtisadiah, Ilaf and Al-Ekhbariah news channel.
Al-Tunisi has a master's degree in information from a US university.
