"All candidates must benefit from the constitutional principles of equal treatment," said a statement from the Diomaye President coalition.
"That's why the release without delay of candidate Bassirou Diomaye Diakhar Faye is a popular demand and respectful of the Constitution," the statement said.
The coalition noted the situation also required the urgent release of jailed opposition Pastef party leader Ousmane Sonko.
The Constitutional Court rejected Sonko's candidacy but accepted that of Faye, the party's number two, along with about 20 others.
Sonko has been in prison since July 2023 for calling for an uprising, associating with criminals linked to terrorism and harming state security.
Faye has been under preventive detention since April last year but has yet to face trial.
The European Union last month stressed that candidates approved by the Constitutional Council must all be allowed to campaign for election on equal terms.
Dozens of opposition supporters have been set free in recent days by President Macky Sall who says there are no political prisoners in Senegal.
The Diomaye coalition called for "all political prisoners who have been locked up unjustly to be immediately released."
Sall plunged traditionally stable Senegal deep into crisis by postponing at the last minute the February 25 election for his successor.
In power since 2012 but not running for a third term, Sall said he called off the vote over disputes about the disqualification of potential candidates and concern about a return to unrest seen in 2021 and 2023.
The Constitutional Council intervened on Thursday and Sall, under strong international and domestic pressure, back-pedaled agreed to its demand to organise the election as soon as possible, but no date was set.
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