GAO, Mali (Reuters) - Gunfire and explosions were heard on Thursday in Mali's northern town of Gao, where French and Malian troops have been working to secure the area against bombings and guerrilla attacks by Islamist rebels, witnesses said.

Reuters journalists in Gao said there was automatic rifle fire and the detonations of heavier weapons and explosions.

French and Malian military spokesmen were not immediately available to comment on the firing and its cause.

(Reporting by Emanuel Braun and Joe Penney; Editing by Pascal Fletcher)