PARIS — France’s top defense official said Tuesday that his country is continuing to build up its forces inside the West African nation of Mali and that the Malian military so far had been unable to rout Islamist rebels from the strategic city of Konna, which al Qaida-linked insurgents seized last week, or from the village of Diabaly, which fell to the rebels on Monday.

The Islamists "remain agile, motivated, well-equipped, well-trained and able to hide in the mountains and vegetation," French Defense Minister Jean-Yves Le Drian told reporters.

The assessment, on the fifth day into the French intervention in Mali, was less optimistic than previous reports of fighting, which had suggested that French air attacks had sent rebel forces reeling. The French assault began Friday after Islamist insurgents seized Konna, prompting a call for help from the Malian government to both France and the United Nations.

Then on Monday, insurgents overwhelmed the rice farming village of Diabaly, about 215 miles north of Bamako, Mali’s capital, surprising both the French and Malian government officials.

Day and night bombing raids had not dislodged the rebels from the Diabaly, Le Drian said, and a convoy of French troops was reported to be on the way to the village.

A ground offensive on Diabaly would be the first infantry foray by French forces, which until now have confined their intervention to air assaults in support of Malian troops on the ground.

Le Drian said Malian soldiers have been "severely tested" in combat with the al Qaida-affiliated Islamists, who he said are far from “having given up their fight.”

French Defense Chief of Staff Adm. Edouard Guillaud said the rebels are well armed but that French officials do not believe they have portable surface-to-air missiles.

French aircraft have flown 50 missions against enemy positions, Guillaud said, some involving attacks on multiple targets.

Le Drian said France now had 1,700 French troops committed to the Mali operation, and that more were on the way. One French company of light armored vehicles, about 30 in all, also arrived Tuesday in Bamako.

He said 12 fighter aircraft, including two Mirage F-1CR, six Mirage 2000D and four Rafale jet fighters were involved in the air operations and that five C-135 tankers aircraft were involved in refueling. All the aircraft are stationed at a French base in N’Djamena, Chad.

Le Drian added that West African nations have pledged to contribute a total of 2,900 troops to the effort, though none has arrived yet.