SEVARE, Mali – Islamic extremists based in the Malian town of Ansongo have destroyed a bridge near the Niger border, officials said on Friday, marking the first use of explosives by the insurgents since the start of a French-led military intervention two weeks ago.

The explosion shows that the extremists remain a nimble and daunting enemy, despite gains by the French, who have recaptured three towns from the insurgents and on Friday pushed toward the Islamist stronghold of Gao, one of three provincial capitals controlled by the al-Qaida-linked rebels.

Djibril Diallo, the village chief of Fafa, located 12 miles from the bridge, said by telephone on Friday that residents of his town had called him to confirm that members of the Movement for the Oneness and Jihad in West Africa had traveled toward the border with Niger to the outskirts of Tassiga on Thursday, before destroying the bridge crossing into the town. The rebel group, also known as MUJAO, traveled from the locality of Ansongo, roughly 25 miles from Tassiga.