French and Malian troops secured the north Mali town of Bourem on Sunday, tightening their control over areas where Islamist insurgents have been launching guerrilla attacks to harass the French-led military operation.
"Bourem is a bastion of Islamists," said a military official from an African military contingent called AFISMA.
African troops in this contingent are being deployed behind the French forward lines in the five-week-old intervention by Paris in its former Sahel colony.
Located by the Niger River, Bourem is about 80 km (50 miles) north of Gao at a crossroads between Timbuktu to the west and Kidal to the north, both of which are now under French and Malian government control.
"All the current problems in Gao come from Bourem," said the official, who asked not to be named. He said there had been no real fighting to take the town.
French leaders have said they intend to start pulling out the 4,000 French troops in Mali in March to hand over security to the Malian army and to the U.N.-backed AFISMA force, which is expected to exceed 8,000 soldiers and is drawn mainly from Mali's West African neighbors.
Last week two suicide bombers struck at the same checkpoint on the road coming into Gao from Bourem, while insurgents also launched a surprise raid in Gao battling French and local troops.
The attacks, two weeks after Gao was liberated from al Qaeda-allied rebels who had held it for 11 months, surprised the French and the Malian soldiers there and raised the prospect of a laborious counter-insurgency task for Paris' forces.
After driving the jihadist rebels from main northern towns such as Gao and Timbuktu, French warplanes and special forces are searching for rebel hideouts in the remote and mountainous northeast, where Paris believes the insurgents may be holding French hostages sized in the Sahel and Nigeria.
The United States and Europe back the French-led operation against al Qaeda and its allies in Mali, hoping it will ward off the threat of jihadist attacks in Africa and elsewhere.
But while providing logistical and intelligence support in Mali, the American and European governments have ruled out sending their own ground troops, and analysts say the French may be left with a messy anti-guerrilla war on their hands.