Some 30,000 people may have been displaced by fighting in central and northern Mali since Islamist insurgents started moving south last week, the United Nations has said.
UN deputy spokesman Eduardo del Bueys said it is feared the number may be even higher as some rebel groups are reportedly preventing Malians from fleeing to the government-controlled south.
He told reporters a total of 230,000 people have been displaced by fighting and insecurity in Mali since March 2012, when the democratically elected president was overthrown by mutinous soldiers in a coup, creating a security vacuum. That led secular Tuaregs, who have long felt marginalised by Mali's government, to take half the north as a new homeland.
But months later they were kicked out by Islamist groups allied with al-Qaida, who took control of the north and have imposed strict Sharia law.
Late last year, the 15 nations in the West African regional group known as ECOWAS, which includes Mali, agreed on a proposal for the military to take back the north.
The Islamists unexpectedly started heading south last week and on Thursday captured the city of Konna, which the weak Malian army was unable to hold. The Islamists appeared to be heading for the nearby city of Mopti, which has 100,000 inhabitants, and the capital, Bamako.
Mali's president asked France for help on Thursday and a day later French troops launched a military offensive against the rebels.
The Islamist fighters responded to French airstrikes and military action with a counter-offensive yesterday, overrunning the garrison town of Diabaly.
France's UN Ambassador Gerard Araud said the government had sought a political solution for the last 12 months but felt it had no choice but to intervene when the rebels took Konna. "Our assessment was that they were totally able to take Bamako - and so we decided that what was at stake was the existence of the state of Mali, and beyond Mali was the stability of all West Africa," he said. "So it's with determination, but also with reluctance, that we have decided that we had no other choice that to launch this military intervention. And we'll conduct it as long as it will be necessary."
He said the Malian army "have suffered heavy casualties but they are fighting - they are fighting in very difficult circumstances". France has received offers of logistical help from the US, Canada, Britain, Denmark, Belgium, and "maybe Germany", he added.