Tunisia's Constitutional Council has announced that under the constitution the speaker of parliament, not the prime minister, should be the interim president.
Prime Minister Mohamed Ghannouchi said yesterday he was taking over as interim president because the incumbent, Zine al-Abidine Ben Ali, was temporarily unable to fulfil his duties.
An analyst said the constitutional council's announcement did not mean there was a conflict over who is standing in as president, but that officials were taking care to act in line with the constitution.
Mr Ghannouchi himself, who this morning was in talks on forming a new government, has issued no reaction to the announcement by the council, the country's highest legal authority on constitutional issues.
The council also said the constitution requires new presidential elections to be held no later than 60 days from now, state television reported.
"The Constitutional Council announces that the post of president is definitively vacant so we should refer to article 57 of the constitution, which states that the speaker of parliament occupies the post of president temporarily and calls for elections within a period of between 45 and 60 days," Fathi Abd Ennather, president of the council said on state television.
Tunisian analyst Nourredine Mbarki said the circumstances had changed since Mr Ghannouchi took over as interim president on last night, so now a different provision of the constitution will apply.
"This is not about a conflict between Mr Ghannouchi and the others," Mr Mbarki said.
"Ghannouchi said he was temporarily president because he was not sure if Ben Ali had fled, or because he thought Ben Ali could resume his post," he said.
"So, once we are sure the president is no longer here and did not leave instructions authorising the prime minister to occupy the post, then automatically the speaker of parliament becomes the interim president."