Zammel, one of three candidates approved to stand in the Oct 6 poll, was taken to a police station outside the capital Tunis, campaigner Mahdi Abdeljaouad told Mosaique FM radio.

Human Rights Watch (HRW) has accused the North African country of blocking rivals of President Kais Saied from standing.

Saied, who is seeking a second term, won power in a 2019 election but orchestrated a sweeping power grab in 2021 and has since ruled by decree.

Abdeljaouad said Zammel was suspected of “falsifying” the endorsement signatures required under Tunisian law to show he has enough support to stand.

The treasurer of his Azimoun party was arrested last month on similar charges and, according to local media, will stand trial on Sept 13.

To appear on the ballot, candidates are required to present a list of signatures either from 10,000 registered voters, 10 parliamentarians or 40 local officials.

Several would-be candidates have been accused of forging these signatures.

HRW has said at least eight prospective candidates have been “prosecuted, convicted or imprisoned”.

In addition to the three candidates already approved to stand, three more have successfully appealed against their disqualification, paving the way for them to run.

The election authority ISIE is due to issue a final list of candidates this week.