BAMAKO, Mali — The battle to retake Mali’s north from the al-Qaida-linked groups controlling it began in earnest Saturday after hundreds of French forces deployed to the country and began aerial bombardments to drive back the Islamic extremists.

At the same time, nations in West Africa authorized the immediate deployment of troops to Mali, fast-forwarding a military intervention that was not due to start until September.

The decision to begin the military operation was taken after the extremists, who seized the northern half of Mali nine months ago, decided last week to push even farther south to the town of Konna, reaching within 30 miles of Mopti, a town that is the site for a major base for the Malian military.

Many believe that if Mopti were to fall, the Islamists could potentially seize the rest of the country, dramatically raising the stakes. The potential outcome was “a terrorist state at the doorstep of France and Europe,” French Defense Minister Jean-Yves Le Drian said Saturday.

France scrambled Mirage fighter jets from a base in neighboring Chad, as well as combat helicopters that began the aerial assault on Friday. The French sent in hundreds of troops to the front line, as well, to secure the capital, Bamako. In just 24 hours, French forces succeeded in dispersing the Is- lamists from Konna, the town the fighters had seized in a bold advance earlier in the week, Le Drian said.

Malian military officials said they were now conducting sweeps, looking for snipers.

“A halting blow has been delivered, and heavy losses have been inflicted on our adversaries, but our mission is not complete,” French President Francois Hollande said after a three-hour meeting with his defense chiefs in Paris. “I reiterate that it consists of preparing the deployment of an African intervention force to allow Mali to recover its territorial integrity.”

However, in a sign of how hard the battle ahead may be, the extremists succeeded in shooting down a French helicopter, the defense minister confirmed. The pilot died of his wounds while he was being evacuated. The Islamists are using arms stolen from ex-Libyan leader Moammar Gadhafi’s arsenal, as well as the weapons abandoned by members of Mali’s military when they fled their posts in the face of the rebel advance.

They have outfitted SUVs with high-caliber machine guns and have released videos displaying their collection of anti-aircraft weapons.

The Islamists have vowed to retaliate against French interests, and they claim to have sleeper cells in all of the capitals of the West African nations that are sending troops.

In a brief televised statement Saturday evening, Hollande said that as a result of the Mali intervention, he had asked for increased security at government buildings and in public spaces in France.

France has some of the world’s most recognizable monuments and a wide-ranging national transportation network; like the U.S., it also has an organized government response if there are specific fears of a terrorist attack.

Online in jihadist forums, participants called for fighters to attack French interests in retaliation for the air raids. They discussed possible targets, including the French Embassy in neighboring Niger, one of the countries donating troops, according to a transcript provided by Washington-based SITE Intelligence.

The sudden military operation is a reversal of months of debate over whether Western powers should get involved in a military bid to oust the militants, who took advantage of a coup in Mali’s capital in March to capture the north. As recently as December, U.N. Secretary-General Ban Ki-moon cautioned against a quick military operation. Diplomats said that September would be the earliest the operation could take place.

All of that went out the window last week when the fighters pushed south from the town of Douentza, which demarcated their line of control, located 540 miles from the capital. By Thursday, they had succeeded in pushing an additional 72 miles south, bringing them nearly face to face with the ill-equipped and ill-trained Malian military in a showdown that couldn’t be ignored by the international community.

In a statement released Saturday, the bloc representing nations in West Africa, ECOWAS, said they had authorized the immediate deployment of troops to Mali. With the fall of Konna and the movement of the Islamist fighters south, ECOWAS Commission President Kadre Desire Ouedraogo said the nations made the decision “in light of the urgency of the situation.”

Most of the ECOWAS troops are expected to originate from Nigeria, Niger, Senegal and Togo and be commanded by a Nigerian general. ECOWAS hopes for some 3,300 troops.

In Washington, a U.S. official confirmed that the U.S. has offered to send drones to Mali. French officials said they had asked Washington to speed up its contribution by sending drones to improve surveillance over the vast area of northern Mali. The French have only two such drones. The Americans are also expected to help with refueling aircraft, and the Pentagon is reported to be studying the French request. A French official close to the presidency said Hollande spoke with the British prime minister, who offered troop-transport aircraft. Neither official could be named because they weren’t authorized to discuss the matter publicly

Lt. Col. Diarran Kone, spokesman for the Malian army, said on Saturday that he was at the Bamako airport to receive a contingent of French special forces from one of their tactical units.

Residents in the town of Sevare, near the line of control, said they had seen planes of white people arriving, who they assume were French soldiers.

Hundreds of French troops were involved in the operation, code-named “Serval” after a sub-Saharan wildcat, officials in Paris said.

“The situation in Mali is serious,” Le Drian, the French defense minister, said in Paris. “It has rapidly worsened in the last few days. ... We had to react before it was too late,” he added.

French intelligence services had detected preparations for what they described as a “major offensive” organized and coordinated by al-Qaida in the Islamic Maghreb and their allies against the towns of Mopti and Diabaly. After a large number of vehicles were spotted heading toward the strategic town on Thursday, France sent in its first unit to Sevare, a town adjacent to Mopti, to support the Malian combat forces, Le Drian said.

Then on Friday, Hollande authorized the use of French air power after an appeal from Mali’s president. French pilots targeted a column of jihadist fighters traveling in trucks who were heading southward toward Mopti from Konna. He said that the helicopter raid led to the destruction of several units of fighters and stopped their advance toward the city.

Overnight Saturday, airstrikes began in the areas where the fighters operate, Le Drian said, led by French forces in Chad, where France has Mirage 2000 and Mirage F1 fighter jets stationed. Residents in the Malian town of Lere, near the Mauritanian border, confirmed that it had been bombed.

Al-Qaida’s affiliate in Africa has been a shadowy presence for nearly a decade, operating out of Mali’s lawless northern desert. They did not come out into the open until this April, when a coup by disgruntled soldiers in Bamako caused the country to tip into chaos.

The extremists took advantage of the power vacuum, pushing into the main towns in the north, and seizing more than half of Mali’s territory, an area larger than Afghanistan.

Turbaned fighters now control all the major northern cities, carrying out beatings, floggings and amputations in public squares just as they did in Afghanistan.

Information for this article was contributed by Rukmini Callimachi, Baba Ahmed, Jamey Keaten, Lori Hinnant, Brahima Ouedraogo and Robert Burns of The Associated Press; and by Steven Erlanger, Scott Sayare and Adam Nossiter of The New York Times.

Front Section, Pages 1 on 01/13/2013