Tunisian presidential candidate Ayachi Zammel was still in detention on Friday despite being released for a few hours a day earlier, his campaign team said.

Zammel is one of three candidates approved by Tunisia's electoral commission to run in a presidential election on October 6 which opposition critics say is rigged in favour of President Kais Saied.

Authorities have accused him of election-related irregularities.

He was first arrested on Monday and a judge ordered him set free on Thursday.

State news agency TAP reported on Friday he had been freed from police custody, referring to his first release before he was re-arrested.

His campaign team told Reuters he was still in custody on Friday. Mahdi Abdel Jawed said: "Zammel is still under arrest since last night, just minutes after he was released."

He is accused of falsifying voter forms for next month's election. Each candidate must submit forms from 10 000 supporters to qualify to stand. He denies the allegation.

Zammel has said he faces restrictions and intimidation because he is a serious competitor to Saied. He has pledged to rebuild democracy, guarantee freedoms and fix Tunisia's collapsing economy.

Saied was democratically elected in 2019, but then tightened his grip on power and began ruling by decree in 2021 in a move the opposition has described as a coup.

Major political factions say Saied's years in power have eroded the democratic gains of Tunisia's 2011 revolution.

Opposition parties and human rights groups have accused the authorities of using arbitrary restrictions to help ensure Saied's re-election.

Along with Zammel and Saied, politician Zouhair Maghzaoui is approved to run in the election.