Ivory Coast said it is strengthening security along its northern border in response to "unusual refugee flows" thought to be caused by armed groups' attacks on civilians in neighbouring Mali, which is battling a jihadist insurgency.

Ivory Coast's National Security Council instructed the military leadership to reinforce security in the area after a meeting on Thursday, a government statement said.

The rise in the number of refugees is "reportedly due to attacks on civilians by Armed Terrorist Groups in several localities in southern Mali," the statement said, adding that Ivorian authorities were working to register asylum seekers.

The statement did not specify which armed groups were behind the violence.

Landlocked Mali is battling al Qaeda-linked jihadists who in September announced a fuel blockade that has led to long lines at petrol stations in the capital and temporarily forced schools to close.

The latest show of force by the group, Jama'at Nusrat al-Islam wal-Muslimin (JNIM), has raised concern abroad that it might eventually try to impose its rule over the country.

JNIM has expanded operations in western Mali while also advancing in the south towards Ivory Coast.

Mali's foreign minister this week dismissed as implausible the notion that jihadists could soon take the capital Bamako.

More than a decade of insurgencies in the Sahel has displaced millions and battered economies, prompting Ivory Coast and other coastal nations to invest heavily to push militants back.