West African neighbours Mali, Burkina Faso and Niger have announced a new 0.5% levy on imported goods as they seek to fund a new three-state union after leaving the larger regional economic bloc, they said in a statement.

The Alliance of Sahel States began in 2023 as a security pact between the military rulers of the three countries, who all took power in coups in recent years. It has since grown into an aspiring economic union with plans for biometric passports and closer economic and military ties.

The levy was agreed on Friday and will take effect immediately. It will affect all goods imported from outside the three countries, but will not include humanitarian aid, the statement said. It will "finance the activities" of the bloc, it said, without giving details.

The move ends free trade across West Africa, whose states have for decades fallen under the umbrella of the Economic Community of West African States (ECOWAS), and highlights the rift between the three states that border the Sahara Desert and influential democracies like Nigeria and Ghana to the south.

The juntas of the three countries announced plans to leave ECOWAS last year, accusing the bloc of failing to assist in their fight against Islamist insurgents and ending insecurity.

ECOWAS had imposed economic, political and financial sanctions on the three in a bid to force them to return to constitutional order, to little effect.

Mali, Burkina Faso and Niger are some of the poorest countries in the world and have been overrun by an armed Islamist insurgency over the past decade.

The violence, committed by groups linked to al Qaeda and the Islamic State, has killed thousands, forced millions to flee, and eroded faith in the democratically elected governments that initially struggled to contain it.