Sporadic heavy weapons fire rang out in the northern Malian town of Kidal overnight and on Saturday, in a sign that a Tuareg-led rebellion was nearing its most significant target to date after two weeks of fighting.
Rebels combining veteran Tuareg insurgents and returnees from Libya's war last year are fighting to create an independent state in north Mali. They have gained ground in a three-pronged advance, scattering thousands across Mali's desert north and beyond its borders, but Kidal is the most significant town yet to be threatened.
Hama Ag Sid'Ahmed, a Europe-based spokesman for the rebels, said the attack had already begun. We will take the two military camps and occupy the town.
However military sources in Kidal and the capital, Bamako, said the sound of gunfire came from army units warding off a rebel attack following rumours that the MNLA would strike at some stage on Saturday.
A Reuters journalist in the town confirmed hearing heavy weapons fire overnight but was unable to say who was firing.
Civilians fearing an attack have been fleeing Kidal by bus in recent days. Some Tuareg say many of their community have also fled Bamako, in the south, fearing reprisals after violent demonstrations this week.
About 3,500 people had crossed westwards into Mauritania, said a Mauritanian official, who asked not to be named.
The International Committee for the Red Cross said on Friday that nearly 10,000 people had fled into Niger after fighting between the army and armed groups in the area around Menaka and Anderamboucane, in the northeast of Mali.
One refugee in Niger, Aminatou Sango, said everyone tried to flee. I left my very old mother and one of my daughters as they could not walk. I am here alone.
The rebels say they are fighting to secure the independence of Azawad, an area that takes in Mali's three northern regions, one of which is Kidal. The government accused the rebels of atrocities and collaborating with al Qaeda, a charge rejected by the MNLA.
The ICRC said that some refugees were being looked after by local families while others had set up makeshift camps nearby.
But the organisation warned that the refugees were crossing into a desert region of Niger that is expected to be hit hard by a food crisis this year.
(Additional reporting Tiemoko Diallo in Bamako and Nathalie Prevost in Sinagodor; Additional reporting and writing by David Lewis; Editing by Ben Harding)