Officials in Mali say one person was killed and three injured when the northern city of Gao came under fire from unidentified assailants.

Radhia Achouri, a spokeswoman for Mali's U.N. mission, said the attack occurred at around 6 a.m. Sunday and that three people were injured.

The superintendent of Gao's hospital, Ibrahim Maiga, said one woman was killed.

Residents said about six shells were fired.

Like other cities in northern Mali, Gao came under control of Islamic extremists linked to al-Qaida following a military coup in 2012. A French-led intervention in early 2013 scattered the extremists but did not drive them out entirely, and Mali's north remains insecure.

An attack last month on a restaurant in the southern capital, Bamako, raised fears that the militants could be extending their reach.