Three West African states ruled by military leaders have announced visa-free travel and residency rights for citizens in the 15-member regional bloc Ecowas, ahead of the trio leaving the group.

The leaders of the states - Burkina Faso, Mali and Niger - said the visa and residency decision had been taken in the spirit of friendship, and to strengthen centuries-old ties among African people.

The trio plan to withdraw from Ecowas in January after refusing the bloc's demand to restore democratic rule.

Ecowas leaders are meeting in Nigeria to discuss the decision, with fears their withdrawal would be a major blow to regional unity and efforts to boost economic and security cooperation.

At the opening of the summit, Ecowas commission head Omar Touray said their "impending exit" was "disheartening", but he wanted to "commend the ongoing mediation efforts", AFP news agency reported.

Senegal's President Bassirou Diomaye Faye has spearheaded efforts to persuade the military juntas to remain in the bloc, but they have refused.

After a ministerial-level meeting on Friday in Niger's capital, Niamey, the three states said in a joint statement that their decision was "irreversible".

Burkina Faso, Mali and Niger were founding members of Ecowas in 1975.

With their planned departure, the bloc will lose 76 million of its 446 million people and more than half its total geographical land area.

This is the first split in Ecowas, with the three breakaway states forming their own bloc, the Alliance of Sahel States.

In a statement, the new alliance's chairman, Mali's military ruler Assimi Goïta said the right of Ecowas citizens to "enter, circulate, reside, establish and leave the territory" of the new bloc would be maintained.

His statement was seen as a signal to Ecowas leaders that Burkina Faso, Mali and Niger wanted to maintain good relations, despite quitting the bloc.

The three states gave notice to Ecowas in January 2023 that they will withdraw in a year, meeting the timeline set by the bloc for states that decide to leave.

Relations between the bloc and the three countries have been tense after military coups took place in Niger in July, Burkina Faso in 2022 and Mali in 2020.

Ecowas condemned the coups, and suspended their membership, hoping they will restore civilian rule.

But the coup leaders dug in their heels, and have pivoted towards Russia.

They accuse Ecowas of being too close to Western powers, and are increasingly relying on Russia to fight armed jihadists who are waging an insurgency in the region.