French troops have encircled a key Malian town to stop radical Islamists from striking closer to the capital, a French official said.
The move to surround Diabaly came as French and Malian authorities said they had retaken Konna, the central city whose capture prompted the French military intervention last week.
The United Nations warned that some 700,000 civilians could be displaced by the fighting in Mali, where the French-led international force is fighting to oust the rebels from power in the north.
The French forces moved around Diabaly to cut off supplies to the Islamist extremists, who have held the town since Monday, said a French official.
The Malian military chased the Islamists from Konna and are now holding the town, a Malian military official said.
Telephone lines were cut off in the town, making it difficult to independently verify the claim though the French official also confirmed the rebels no longer hold Konna.
Doctors Without Borders have been trying to get to Konna since Monday but all roads leading to the community in central Mali have been closed by the Malian military, said Malik Allaouna, director of operations for the group known as MSF.
"Despite our repeated requests, we are still being refused access to the Konna region," he said. "It is essential to allow the delivery of neutral and impartial medical and humanitarian aid in the areas affected by the conflict."
In Geneva, United Nations refugee agency spokeswoman Melissa Fleming said that the number of displaced Malians is expected to increase dramatically in the coming months.
Those who have fled "mentioned that large amounts of money are being offered to civilians to fight against the Malian army and its supporters", she said.
Meanwhile, authorities in the town of Niono said that a key road leading to Segou was being closed to traffic today.
Segou is one of the largest towns in Mali and the administrative capital of its central region. The road closure is an attempt to keep Islamists from entering towns further south, officials said.
The prefect, or district administrator, of Niono, Seydou Traore said "neither cars, nor motorcycles, nor people on foot will be able to travel, as a security measure".
France has encountered fierce resistance from the extremist groups, whose tentacles extend not only over a territory the size of Afghanistan in Mali, but also another 600 miles to the north east in Algeria, where fighters stormed a BP-operated plant and took dozens of foreigners hostages.
They demanded the immediate end of the hostilities in Mali, with one commander, Oumar Ould Hamaha, saying that they are now "globalising the conflict" in revenge for the military assault on Malian soil.
Yesterday, France increased its troop strength in Mali to 1,400, said French defence minister Jean-Yves Le Drian.
West African neighbours also have begun sending troops to aid the French-led mission, with some Togolese and Nigerian forces arriving yesterday.
Nigeria has offered another 900 soldiers, while Chad has said it will send 2,000 to aid the mission.
A former French colony, Mali once enjoyed a reputation as one of West Africa's most stable democracies with the majority of its 15.8 million people practising a moderate form of Islam. That changed last March, following a coup in the capital which created the disarray that allowed Islamist extremists to take over the main cities in the distant north.