Islamic extremists who control the northern half of Mali on Saturday captured their furthest position south in the town of Douentza, which frontiers government-held territory.
Fighters from a group allied to Al-Qaeda in the Islamic Maghreb (AQIM) entered the town in a convoy of 4x4s and disarmed a local militia, witnesses said.
Douentza lies 170 kilometres (100 miles) from the town of Mopti, the last big army-controlled town en route to the north, which was seized by armed Islamist groups linked to AQIM in March and April.
Local teacher Moussa Dicko told AFP the Movement for Oneness and Jihad in West Africa (MUJAO) had entered the town on Saturday morning.
"This morning between 7:00am (local and GMT) and 8:00am people from MUJAO arrived on nine 4x4 vehicles. They disarmed people from Ganda Iso" (Sons of the Land), a local militia which was holding the town.
"They took all the weapons and then chased them away," said Dicko, adding that the jihadists had met officials in the town to explain that the self-defence group -- which had promised to work with them -- were "traitors".
"As I speak they have taken the different entrances and exits to the town."
Farmer Almadhi Cisse confirmed the information.
"This morning when I woke up I saw MUJAO vehicles heading towards the barracks. A while later I heard all the people from Ganda Iso had been disarmed. No one was killed. Now they are at the eastern and western entrances to the town."
Douentza -- which lies on the route to the fabled city of Timbuktu -- was first captured in early April by separatist Tuareg rebels from the National Movement for the Liberation of Azawad (MNLA).
The Tuareg, who claim Azawad as their homeland, shortly afterwards declared independence of the northern triangle of the bow-tie shaped nation.
The west African country, which was considered one of the regions' most stable democracies, has plunged into crisis since the Tuareg kicked off their rebellion in January.
The desert nomads, boosted by the return of fighters from Libya, quickly overwhelmed Mali's army in the vast desert region which is larger than France, or Texas.
Frustrated by their rout and feeling abandoned by Bamako, angry soldiers overthrew President Amadou Toumani Toure's government on March 21.
The military overthrow sparked chaos which allowed the Tuareg to complete their takeover of the north, aided by armed jihadist groups allied to Al-Qaeda in the Islamic Maghreb (AQIM) in search of a state run under strict Islamic law.
Having piggy-backed on the Tuareg rebellion, the Islamists soon chased their erstwhile MNLA allies out of all key posts and have proceeded to enforce sharia law.
The MNLA also abandoned their posts in Douentza after their defeat, and in the absence of any military presence, Ganda Iso has since held the town.
Several self-defence groups have sprung up in Mali in frustration over government's slow response to the Islamist takeover, drawing volunteers from all walks of society.
Many of them are aligned with Ganda Iso, a militia historically backed by the army, that is known for deadly past attacks against lighter-skinned Tuareg or Arab Malians.
In the small town of Soufouroulaye, near Mopti, nearly 300 civilian militia volunteers are being trained by soldiers, AFP witnessed recently.
In the capital Bamako a similar militia opposed to the Islamic occupation, Bouyan Ba Hawi ('Better death than shame' in the Songhoi language) was dismantled this week and its leaders arrested.
Five months after the occupation, it is not clear when or if any military intervention will take place to win back the north, with some still hoping talks can resolve the crisis.
Mali's interim authorities appear loathe to accept an offer of 3,300 regional troops from the Economic Community of West African States, insisting its poorly-equipped army will play the lead role in ejecting the jihadists.