Senegalese police on Wednesday detained former interior minister Ousmane Ngom for questioning while on the campaign trail for upcoming legislative polls, a police source said.

"Police officers went to Kolda (south) to take him in," the source said without giving the reasons for Ngom's detention.

The ex-interior minister, with the Senegalese Democratic Party (PDS) was taken in by an elite police unit in the southern Senegalese town of Kolda where he was campaigning ahead of July 1 legislative polls.

"He was not ill-treated by police," reported the Senegalese news agency APS.

Ngom was among several officials from Abdoulaye Wade's former regime who were recently summoned for questioning in relation to a probe into ill-gotten gains.

However he had left the courthouse after a long wait to be questioned.

Ngom came under fire during March presidential elections for the repression of opposition protests which sparked near-daily riots in Dakar amid anger over Wade's disputed bid for a third term in office.

Wade was roundly beaten at the ballot box by Macky Sall in a second round of voting.

Sall's new government recently opened a special court to look into fraud and ill-gotten gains.

"Those who have done nothing wrong must be calm because nothing can happen to them. We are not a banana republic," Sall said recently.

Wade said he was "willing" to undergo audits by the new authorities after a presidency dogged by financial scandals but has heavily criticised the probe into ill-gotten gains which saw police seize scores of his cars.

"You don't summon a minister like he is a vulgar individual and ask him whatever about his management," Wade said in an interview last week, warning he would disrupt the legislative elections if he did not get his cars back.