French forces have taken control of an area around the airport and bridge in Gao, a city in north-eastern Mali that for months has been controlled by al Qaida-linked extremists.
France's defence minister, Jean-Yves Le Drian, announced that jihadist fighters who encountered advancing French and Malian troops "saw their means of transport and their logistics sites destroyed".
There was no immediate word on possible casualties.
Gao has long been under the control of the al Qaida-linked Movement for Oneness and Jihad, or MUJAO. Phone lines in the city have been cut for days.
The move comes just two weeks after France launched its military offensive to rout the Islamists from power in northern Mali.
The Islamists first seized control of Gao and two other provincial capitals - Timbuktu and Kidal - in April last year during the chaotic aftermath of a coup in the distant capital.
The French and Malian forces launched the air and land operation to take Gao's bridge and airport under the cover of darkness overnight, said Col Thierry Burkhard, a French military spokesman in Paris.
French and Malian forces came under fire in the morning from rebels in Gao and continued to face sporadic "acts of harassment" in the afternoon, Col Burkhard said.
On Friday, in a show of might, the Islamists destroyed a bridge near the Niger border with explosives.
Since France began its military operation two weeks ago, the Islamists have retreated from three cities in central Mali: Diabaly, Konna and Douentza. They have maintained control of the majority of the territory in Mali's north, most importantly the cities of Gao, Kidal and Timbuktu.