When the bombs rained down, the people of Konna rushed to hide. Some flung themselves into the river. Many did not survive – including three children who drowned in the river as they struggled to escape.

The children were among the first civilian casualties of a rapidly escalating military offensive. French warplanes launched attacks on at least five towns in central and northern Mali on the weekend, and there are growing fears that civilians could be caught in the middle of the fighting.

France's hasty military operation, which scuttled a plan for a gradual buildup of carefully trained African ground forces, was triggered by a sudden southward push by the Islamist rebels who already control the northern two-thirds of Mali and were threatening to move southward to capture key cities in the centre of the country.

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Western governments, including Canada, are deeply worried that the Islamist rebels could provide a major African stronghold for terrorist groups such as al- Qaeda, which already has an affiliate in Mali.

But the abrupt French intervention, without waiting for the planned West African ground force, is a risky gamble. It means that the operation will depend largely on air strikes – and civilians could pay a heavy price.

The United States is providing satellite intelligence and logistical help to the French operation, while Britain is providing two military transport planes. Canada is not directly supporting the war in Mali, but a unit of Canadian special forces with weapons and ammunition has landed in neighbouring Niger to begin training its soldiers. Niger is contributing 500 troops to the fight against Mali's rebels.

The civilian toll is mounting. At least 11 civilians have been killed and many others injured in Konna, a town in central Mali that has faced a heavy bombardment by French warplanes since Friday. The town was captured on Thursday by Islamist fighters who inflicted heavy casualties on Malian troops.

Reports from other towns are hazy so far, but there could be significant casualties. In one town under aerial attack, Douentza in central Mali, injured civilians can't even reach the hospital, according to Médecins Sans Frontières (Doctors Without Borders).

"Because of the bombardments and fighting, nobody is moving in the streets of Douentza and patients are not making it through to the hospital," said a statement by MSF emergency response co-ordinator Rosa Crestani. "We are worried about the people living close to the combat zones."

The original plan, approved by the United Nations and the European Union, would have postponed the battle against the Islamists until at least September or October. That would have allowed a gradual buildup of about 3,300 West African troops in Mali, along with a contingent of 250 military trainers from the EU, to support Mali's weak and disorganized army.

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The training and troop buildup should have taken months, so that Mali's army would have a chance to defeat the estimated 3,000 rebels in the Islamist militia groups. Instead, the French air strikes were swiftly launched on Friday when the rebels were on the verge of capturing the crucial towns of Mopti and Sévaré in central Mali.

Since then, France has sent about 400 troops to Mali, but most will remain in the capital, Bamako. Several nations in West Africa promised on Sunday to accelerate the deployment of their troops in Mali, but it could still take weeks for their troops to arrive.

The French intervention was so hasty that it did not wait for any clear approval from the UN. The UN Security Council, in a resolution on Dec. 20, said the international military campaign in Mali would need to be "further refined" and "confirmed in advance" with UN Secretary-General Ban Ki-moon. But there is no evidence that France consulted Mr. Ban before launching its air strikes.

The French air strikes have reportedly driven out the Islamist fighters from Konna and the key northern town of Gao, where many targets were hit, including rebel training camps, air hangars and logistics depots.

French defence minister Jean-Yves Le Drian said the attacks by France's state-of-the-art Rafale and Mirage fighter jets were essential to "eradicate these terrorists" who could threaten Europe's security.

The military operation against the Islamist fighters could continue for months in the vast harsh terrain of the Sahara in northern Mali. The rebels have already killed at least 11 Malian soldiers and shot down at least one French helicopter, killing a French pilot.

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"What has really struck us is how up-to-date their equipment is, and the way they've been trained to use it," a French presidential official told Agence France-Presse.

"At the start, we thought they would be just a load of guys with guns driving about in their pick-ups, but the reality is that they are well-trained, well-equipped and well-armed. From Libya they have got hold of a lot of up-to-date sophisticated equipment, which is much more robust and effective than we could have imagined."

Steven Chase in Ottawa contributed