Malian police arrested 21 activists on Monday accused of planning a march against a proposed compromise deal between the government and Tuareg rebels which would pave the way for nationwide elections.
The arrests come with talks taking place in the Burkina Faso capital Ouagadougou to persuade the National Movement for the Liberation of Azawad (MNLA), who want autonomy for their homeland, to back the polls planned for July 28.
Among those detained in Bamako is Mamoutou Diabate, chairman of Mali's influential Forum of Civil Society Organisations (FOSCM) umbrella group.
"We wanted to organise a march on Monday to protest against the Ouagadougou agreements under way that are too generous to Tuareg rebels who slaughtered the Malian military," Amadou Malle of FOSCM told AFP.
"We are accused of disturbing public order. There is no disorder. We want to defend our country, that's all."
Malian police refused to comment on the arrests.
Flush with weapons following the return of Tuareg mercenaries who fought alongside slain Libyan tyrant Moamer Kadhafi, the secular MNLA launched an offensive in the north in January 2012.
A March coup by renegade soldiers in Bamako allowed it to conquer the northern half of the country but it was soon overpowered by groups with ties to Al Qaeda.
Former colonial power France sent in jets and troops in January 2013 and chased extremist fighters out of the main cities.
The French then let the MNLA back into Kidal, raising fears in Bamako, 1,500 kilometres (930 miles) to the southwest, that Paris wants to let the separatists keep the city as part of a deal for self-rule for the northern desert territory they call Azawad.
The militants were initially reluctant to let government troops step in to secure Kidal for a planned July 28 ballot but agreed to the deal after amendments were made.
International mediators failed on Wednesday to convince Mali's interim president Dioncounda Traore to sign the agreement however, with the talks now expected to take several more days.
Mali remains under a state of emergency which outlaws public protests but an AFP journalist saw a demonstration against the Ouagadougou talks around a kilometre from the station where the activists were detained.
Protesters waved banners bearing a variety of slogans denouncing the negotiations, including "Tuareg rebels = terrorists" and "France = MNLA accomplice".