Gunmen have freed four election workers and a deputy mayor a day after they were kidnapped in Mali's northern town of Tessalit, a local official said.

"The five hostages were picked up this morning by French soldiers outside the town. We do not know what led to them being freed," Cheick Fanta Mady Bouare, the prefet of Tessalit, told Reuters news agency.

An official at the ministry for territorial administration had earlier said that two poll workers had been freed.

The workers were seized on Saturday from the town hall in Tessalit, a remote town about 200km north of the flashpoint northern city of Kidal, where they were planning the distribution of ID cards to registered voters.

The abductions come as Mali's government tries to extend its authority over the country's vast north following last year's coup and a French-led operation against Kidal-based ethnic Tuareg rebels who have agreed to relinquish their claims of independence and allow Mali to hold presidential elections on July 28.

A Malian security ministry official said the kidnapping appeared to be the work of the minority-Tuareg rebel group, the National Movement for the Liberation of Azawad (MNLA).

The MNLA took control of Kidal in February after a French-led operation ousted local and al-Qaeda-linked fighters who had seized control of most of northern Mali.

The Malian authorities finally reclaimed the city after signing a deal with the MNLA and another Tuareg group on June 18 aimed at reuniting the country and clearing the way for elections.

Under the deal, MNLA forces moved into barracks as 150 regular Malian troops were deployed to secure Kidal in the run-up to the vote.

Source: Agencies