French airstrikes in Mali have halted the advance of Islamist rebels in the key town of Konna, France's president said.
Francois Hollande described the military action on Saturday evening, after West African nations had authorised the deployment of more troops to the country.
As more than 100 people - including rebels and government soldiers - were reported to have been killed in the fighting, Hollande vowed to step up security on French soil.
Earlier, French Defence Minister Jean-Yves Le Drian said a French helicopter had been downed on Friday and that the pilot died of his wounds while he was being evacuated to safety.
The al-Qaeda-linked fighters, who have carved out their own territory in the lawless desert region of northern Mali over the past nine months, recently pressed closer to a major base of the Malian army.
"The threat is a terrorist state at the doorstep of France and Europe," said Le Drian.
The fighting involved hundreds of French troops and overnight airstrikes on three rebel targets, said Le Drian, who added that a rebel command centre outside Konna was destroyed.
The French operation, which started on Friday in the former French colony, came after an appeal for help from Mali's president.
"It was only two months ago that [French President] Francois Hollande said there would be no combat troops on the ground," said Al Jazeera's Rory Challands, reporting from Paris.
"By yesterday evening, he said not only were French troops being sent to Mali, but that they were already there. Things are moving incredibly fast."
A military official in Mali said the fighters had been driven out of Konna, but that the city, which was captured by the rebels earlier this week, was not yet under government control.
"We are doing sweeps of the city to find any hidden Islamist extremist elements," said Lieutenant Colonel Diarran Kone.
"The full recovery of the city is too early to determine as we do not yet control the city, and we remain vigilant."
'Urgency of the situation'
During a press conference on Saturday evening, Hollande said: "I remind you that France in this operation is not pursuing any special interest other than securing a friendly nation - and has no other objective."
Hollande on Friday had said the "terrorist groups, drug traffickers and extremists" in northern Mali "show a brutality that threatens us all". He vowed that the operation would last "as long as necessary".
He has said the operation is aimed in part at protecting the 6,000 French citizens in Mali, seven of whom are being held captive.
Sanda Abou Mohamed, spokesman for Islamist group Ansar Dine, told Al Jazeera: "The terrorist French military bombed Konna. The hospitals are now filled with the injured - women, children and the elderly are the main victims."
"It's impossible to know how many have been killed, but the number is huge," he said. "Only five of those killed were our fighters. The rest are all innocent civilians."
Kadre Desire Ouedraogo, the Economic Community Of West African States (ECOWAS) commission president, said on Saturday that the bloc had authorised the immediate deployment of troops to Mali.
He said they made the decision "in light of the urgency of the situation".
ECOWAS did not say how many troops would be sent to Mali or when they would arrive. It also did not specify which countries from the 15-nation bloc would be providing the forces.
The organisation has been talking for months about a military operation to oust the rebel groups from northern Mali. While the UN approved a plan for deployment, it had not been expected until September.
Al-Qaeda's affiliate in Africa has been a presence for years in the forests and deserts of Mali, a country hobbled by poverty and a relentless cycle of hunger.
"The rebels in the North had decided to make a move," political analyst Sylvain Touati told Al Jazeera. "They had the footprint of soldiers who came back from Gaddafi's [army] to northern Mali ... with the momentum to make an offensive."
"Now the French army is trying to maintain the [previous] situation, and training together with ECOWAS for an offensive in the coming months."