Heavy machinegun fire as Malian troops assault the office of the mayor in the northern town of Gao on Thursday.

They're trying to dislodge suspected Islamist gunmen holed up inside.

French and Malian troops have been working to secure the area against bombings and guerrilla attacks by Islamist rebels.

(SOUNDBITE)(French) MALIAN ARMY COMMANDER, SAYING:

"We're dealing with an infiltration from last night, just before the power was cut some elements infiltrated the town and they are trying to take this (building) as well as other assets in the neighbourhood."

Gao is the biggest town in northern Mali.

It was retaken from al Qaeda-linked Islamists last month in a lightning French offensive in cooperation with Mali government forces.

Thursday's clashes came nearly two weeks after French and Malian forces fought hours of street battles with Islamists who had infiltrated the town.