ABUJA, Oct 25 (Reuters) - Nigeria's Supreme Court on Thursday nullified the election in the oil-producing Niger Delta state of Rivers, the third major indictment of April's vote this month.
The elections were meant to be a democratic milestone for Africa's most populous country, but they were so marred by fraud and violence that international observers said they were "not credible".
The Supreme Court ruled Chibuike Rotimi Amaechi, who won the primaries for the ruling People's Democratic Party (PDP) in December, was the lawfully elected governor of Rivers, not Celestine Omehia.
Omehia did not win the primary but his name replaced Amaechi's on the ballot as the PDP candidate in the April 14 vote.
The ruling has the potential of sparking a fresh wave of trouble in Africa's oil heartland, where politicians are backed by rival armed groups.
Omehia's removal came days after another court nullified of the election of Saidu Usman Dakingari, a son-in-law of President Umaru Yar'Adua, on Saturday as the governor of the northwestern state of Kebbi.
Dakingari, who defected from an opposition party shortly before the elections, was not a member of PDP when the party nominated him for the polls, the court said. Dakingari has said he will appeal against the ruling.
Another court in the central state of Kogi on Oct. 10 nullified the election of Ibrahim Idris as governor because the electoral body had removed the name of a key opposition party candidate from the ballot. Idris also said he will appeal.