Mali's Defense Minister Soumeylou Boubeye Maiga resigned Tuesday, a week after government troops were defeated by armed rebels in the restive northeastern town of Kidal, a presidential spokesman said.

"Mali's defence minister has offered his resignation and it has been accepted," the spokesman told Agence France Presse.

Tuareg rebels have made further advances in northern Mali and have seized two towns, Kidal and Menaka, the United Nations confirmed on Thursday.

U.N. spokesman Stephane Dujarric told reporters that fighters from the National Movement for the Liberation of Azawad (MNLA) had taken the towns after clashes with Malian government forces.

Tuareg militants fighting the Malian army in the rebel stronghold of Kidal said Wednesday they had taken control of the flashpoint town, taking prisoners.

"We now control the whole town of Kidal, we have prisoners," Mohamed Ag Rhissa, one of the leaders of the National Movement for the Liberation of Azawad, told Agence France Presse by telephone.

Mali's Prime Minister Moussa Mara said Sunday the country was "at war" against terrorists in the rebel-controlled northern city of Kidal after clashes between separatist militants and the Malian army left 36 dead.

"The terrorists have declared war on Mali, so Mali is at war against these terrorists. We will mobilize the resources to fight this war," Mara told Agence France Presse by telephone.

Malian Tuaregs laid waste to public buildings in the northeastern town of Kidal Thursday, in protest at a decision by separatist leaders to end their occupation of state premises, residents said.

The protesters included dozens of women and youths who had been holding a sit-in outside the governor's offices and the local TV and radio offices of state broadcaster ORTM, which the National Movement for the Liberation of Azawad (MNLA) had occupied for about nine months, according to residents and an army source.

A rebel group seeking independence in northern Mali said on Thursday it had appointed an "administrator" to Kidal in a show of strength after French-led troops liberated the town from an Islamist occupation.

The Tuareg National Movement for the Liberation of the Azawad (MNLA) told Agence France Presse that Mohamed Ali Ag Albessaty, previously a local government functionary, would serve as its top official for Kidal.

About 1,800 Chadian soldiers have entered the northern Mali city of Kidal to "secure" what was the last stronghold of Islamist rebels, the French defence ministry said on Tuesday.

A ministry official said French forces, now numbering 4,000 in Mali, also took control and were securing the city's airport following paratrooper reinforcements.