West Africa's regional bloc has named a politician in Guinea-Bissau to lead the transitional government after a coup.

The group met earlier in the week in the West African nation and named Serifo Nhamadjo to the post for one year. He was among a group of presidential candidates who called for a March poll to be annulled, claiming fraud.

Guinea-Bissau was just weeks away from holding a presidential runoff election when soldiers in April attacked the front-runner's home and arrested him along with the country's interim president.

No leader in nearly 40 years of independence has finished his time in office in Guinea-Bissau, a former Portuguese colony on Africa's western coast that has long been plagued by coups.