France called for international support against Islamist insurgents it says are a threat to Africa and the West and acknowledged it faced a long fight against well-equipped and determined militant fighters who seized Mali's vast desert north last year.
After Islamist threats to exact revenge for France's dramatic intervention, an Al Qaeda-linked group claimed responsibility for a raid on a gas field in Algeria in which seven foreigners were kidnapped and a French national killed.
A column of French armoured vehicles moved into position on Tuesday at the town of Niono, 300 km (190 miles) from the capital Bamako. With the Malian army securing the northern region near the Mauritanian border, Islamist fighters were encircled in the nearby town of Diabaly.
French army chief Edouard Guillaud said his ground forces were starting their campaign against the alliance of Islamist fighters, grouping Al Qaeda's North African wing AQIM with Mali's home grown Ansar Dine and MUJWA militant movements.
"In the coming hours - but I cannot tell you if it's in one hour or 72 hours - yes, of course we will be fighting them directly," he told Europe 1 radio.
In Niono, a resident reported seeing French and Malian troops in armoured vehicles heading toward Islamist rebel lines. Fighting was reported in Diabaly but it was not immediately clear if French ground forces were involved.
Mr Guillaud said French military strikes were being hampered because militants were using the civilian population as a shield.
"We categorically refuse to make the civilian population take a risk. If in doubt, we will not shoot," he said. Residents who fled Diabaly confirmed the Islamists had used the towns inhabitants to protect themselves in recent days.
French fighter jets, meanwhile, struck the headquarters of the Islamic police in Niafunke, a small town on the Niger river near the ancient caravan route of Timbuktu, residents said.
Defence Minister Jean-Yves Le Drian acknowledged that France faced a difficult operation, particularly in Western Mali where AQIM's mostly foreign fighters have camps. Mauritania has pledged to close its porous frontier to the Islamists.
"It's tough. We were aware from the beginning it would be a very difficult operation," Le Drian said.
Waiting for African troops
President Francois Hollande said on Tuesday French forces would remain in Mali until stability returned to the West African nation. Mr Hollande said France hoped, however, to hand over to African forces in its former colony, "in the coming days or weeks."
Military chiefs from the West African regional bloc ECOWAS met for a second day in Bamako on Wednesday in a bid to hammer out the details of their UN-mandated deployment.
With African troops facing huge logistical and transport challenges to quickly deploy their troops, Germany promised two Transall military transport planes to fly soldiers from around the region to Bamako.
Mr Hollande's bold intervention in Mali, which has helped to end his reputation for dithering, brings risks for eight French hostages held by AQIM in the Sahara as well as the 30,000 French citizens living across West Africa.
AQIM and Ansar Dine have vowed to take revenge for France's intervention on its interests around the globe.
In Algeria, where AQIM has its roots, militants seized five Japanese nationals, a French citizen and an Irishman from an oil facility in Ain Amenas in southern Algeria on Wednesday, local and diplomatic sources told Reuters. A French national was killed in the raid.
The field, located close to the border with Libya, is operated by a joint venture including BP, Norwegian oil firm Statoil and Algerian state company Sonatrach.
The conflict in Mali raised concerns across mostly Muslim West Africa of a radicalisation of Islam in the region. In Senegal, a traditionally moderate Islamic country, President Macky Sall warned citizens to be vigilant for attacks.
"We must be on the watch in our towns and villages because infiltrations are taking place," he said in a speech on Tuesday. "You will hear foreign preachers talking in the name of Islam. You must denounce them to authorities."
The fighting in Mali, a landlocked state at the heart of West Africa, has displaced an estimated 30,000 people. Hundreds have fled across the border into neighbouring Mauritania and Niger in recent days.
"We were all afraid. Many young fighters have enrolled with them recently," said Mahamadou Abdoulaye, 35, a truck driver who fled from the northern Gao region of Mali into Niger. "They are newly arrived, they cannot manage their weapons properly. There's fear on everybody's face."