A French pilot died on Friday when his helicopter was shot down near the central Mali town of Mopti. Hours later, a French hostage being held by Islamists in Somalia was killed during a bungled rescue attempt unrelated to events in Mali but which highlighted France's conflict with such groups in Africa.
The West African regional bloc ECOWAS has for months lobbied world powers to back its plan to end the nine-month occupation of Mali's north by al Qaeda-linked groups, which have imposed an extreme version of Sharia law on the moderate Islamic nation.
Ivory Coast President Alassane Ouattara, the current chairman of ECOWAS, signed an order on Friday to deploy some 3,300 regional troops under a U.N. mandated operation.
"By Monday by the latest, the troops will be there or will have started to arrive," said Ali Coulibaly, Ivory Coast's African Integration Minister. "Things are accelerating ... The reconquest of the north has already begun."
The bulk of the forces are expected to come from Nigeria, Niger, Senegal and Togo, led by Nigerian Major-General Shehu Abdulkadir.
Burkina Faso, which has tried to mediate talks with some of the Islamist groups, said on Saturday it would rapidly deploy 500 soldiers to Mali to support the mission.
The African-led mission had not been expected to start until September due to difficulties of funding and training troops.
However, Western governments, particularly former colonial power France, voiced alarm after the rebel alliance captured the town of Konna on Thursday in their first major drive towards the capital Bamako since seizing control of the north in April.
With heavily armed Islamist fighters bearing down on Sevare - home to a military base and a strategic gateway on the route to Bamako 500 km (300 miles) to the south - Mali's government appealed for urgent military aid from France.
France responded on Friday with air strikes which turned back the rebel convoy and allowed Malian soldiers to push the Islamists out of Konna, removing the threat they could conquer the whole of the country.
Army chief Edouard Guillaud said France had no plan to chase the Islamists in the north with land troops. Defence Minister Jean-Yves Le Drian said France had sent special forces to Mopti before the strikes and hundreds of troops to Bamako.
Paris has said that the Islamists' seizure of north Mali gave them a base to attack neighbouring countries and Europe.
"Terrorists should know that France will always be there when the rights of a people - those of Mali who want to live freely and in a democracy - are threatened," Hollande said on Friday, adding the operation would last as long as necessary.
The Elysee palace said Hollande had briefed African counterparts by telephone on Saturday about the mission - named "Operation Serval" after an African wildcat.
France's decisive intervention in Mali could endanger eight French nationals being held by Islamists in the Sahara following a string of kidnappings.
A spokesman for one of Mali's rebel groups, Ansar Dine, warned that France's intervention would have repercussions.
"There are consequences, not only for French hostages, but also for all French citizens wherever they find themselves in the Muslim world," Sanda Ould Boumama told Reuters.
The defence ministry said its failed bid overnight on Friday to rescue a French intelligence officer held hostage in Somalia since 2009 was unrelated to events in Mali.
The ministry said the officer and at least one French soldier were killed, but the Harakat Al-Shabaab Al-Mujahideen insurgent group holding Denis Allex said he was alive and held at a location far from the raid.
The French Foreign Ministry stepped up its security alert on Mali and parts of neighbouring Mauritania and Niger on Friday, extending its red alert - the highest level - to include Bamako.
France advised its 6,000 citizens in Mali to leave. Thousands more French live across West Africa, particularly in Senegal and Ivory Coast.
EU foreign policy chief Catherine Ashton on Friday urged an "accelerated international engagement" and said the bloc would speed up plans to deploy 200 troops to train Malian forces.
A U.S. official said the Pentagon was weighing options such as intelligence-sharing with France and logistics support.
Military analysts voiced doubt, however, about whether Friday's action was the start of the final operation to retake northern Mali - a harsh, sparsely populated terrain the size of France - as neither equipment nor ground troops were ready.
"We're not yet at the big intervention," said Mark Schroeder, of risk and security consultancy Stratfor.
More than two decades of peaceful elections had earned Mali a reputation as a bulwark of democracy - an image that unravelled in a matter of weeks after a military coup last March that paved the way for the Islamist rebellion.
Interim President Dioncounda Traore, under pressure for bolder action from Mali's military, declared a state of emergency on Friday. Traore cancelled a long-planned official trip to Paris on Wednesday because of the violence.
"Every Malian must henceforth consider themselves a soldier," he said on state TV.
On the streets of Bamako, residents praised France's action.
"It's thanks to France that Mali will emerge from this crisis," said student Mohamed Camera. "This war must end now."
(Additional reporting by Rainer Schwenzfeier in Bamako, Mathieu Bonkoungou in Ouagadougou, and Joe Bavier in Abidjan; Editing by Daniel Flynn and Robin Pomeroy)