Tunisian police late on Thursday re-arrested presidential candidate Ayachi Zammel, just minutes after he was released from jail on a judge's order, lawyers said.

Zammel is one of three candidates approved to run in the Oct. 6 presidential election, which opposition critics say is rigged in favour of President Kais Saied.

Zammel was arrested on Monday on suspicion of falsifying voter forms. Each candidate must submit forms from 10,000 supporters to qualify for the election. He denies the allegation.

"He was kidnapped by members of the National Guard to an unknown location," Zammel campaign member Mahdi Abdel Jawad told Reuters.

Abdessatar Massoudi and Dalila Ben Mbarek, two lawyers for Zammel, said he was kidnapped immediately after his release from Borj El Amri prison.

Along with Zammel and Saied, politician Zouhair Maghzaoui is approved to run in the Oct. 6 election.

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.

Tunisian opposition parties and human rights groups have accused the authorities of using arbitrary restrictions to help ensure Saied's reelection.

The electoral commission, on Monday rejected an administrative court ruling reinstating three prominent presidential candidates, reinforcing opposition fears that the commission sought to favour the incumbent president.

Law professors, rights groups and political parties said the commission’s decisions threatened to undermine the legitimacy and credibility of the elections and called on it to back down.