ABUJA, Nigeria (AP) -- The three junta-led West African nations of Niger, Mali and Burkina Faso have formally withdrawn from the regional bloc known as ECOWAS, the body said Wednesday, the culmination of a yearlong process during which the group tried to avert its unprecedented disintegration.

Their withdrawal, first announced a year ago, "has become effective today," ECOWAS said in a statement. The bloc, however, said that it has also decided to "keep ECOWAS' doors open," requesting member nations to continue to accord the three countries privileges of membership, including free movement within the region with an ECOWAS passport.

The 15-nation regional bloc Economic Community of West African States was established in 1975 with one goal: "To promote co-operation and integration ... in order to raise the living standards of its peoples, and to maintain and enhance economic stability."

It has since grown to become the region's top political authority, often collaborating with states to solve domestic challenges on various fronts from politics to economy and security.

Some believe ECOWAS is fast losing goodwill and support from many West Africans who see it as failing to represent their interests in a region where citizens have complained of not benefitting from rich natural resources in their countries.

After coming into power, the juntas in Niger, Mali and Burkina Faso announced that they were leaving ECOWAS, and they created their own security partnership, the Alliance of Sahel States, in September.