Nigeria's Supreme Court dismisses five governors
Nigeria's Supreme Court has ordered five of the country's powerful state governors to step down immediately.
It marks the end of a long legal battle about when exactly their terms in office, which last four years, began.
They were from the ruling People's Democratic Party, winning polls in 2007 in Bayelsa, Cross River, Kogi, Adamawa and Sokoto and vote re-runs in 2008.
The BBC's Fidelis Mbah in Lagos says it is a landmark judgement, asserting the authority of the judiciary.
Governors, who can serve no longer than two terms in office, enjoy wide powers in Nigeria.
Some, especially in oil-producing areas, control bigger budgets than those of national governments in some neighbouring West African countries.
'Stopping culture of impunity'
The five governors affected by the ruling had all won re-run elections a year after their initial victories in 2007 were annulled because of irregularities.
Last year, a lower court had exempted them from having to face elections in April 2011, saying their tenures had started in 2008.
But Supreme Court Judge Walter Onnoghen said on Friday: "To allow the governors seeking tenure elongation will allow a culture of impunity in the system", AFP news agency reports.
Our correspondent says the speakers of the respective state House of Assemblies will assume the governorships in Bayelsa and Cross River states in the south and Sokoto and Adamawa in the north until elections are held later in the year.
The central state of Kogi already has a governor-elect following elections in December, as the sitting governor was serving his last term in office.
Liyel Imoke, the outgoing governor of Cross River, said on the social networking site Facebook that he had already vacated his office.
He will be running for a second term and appealed for "calm and peace in the state".
Despite its vast resources, Nigeria ranks among the most unequal countries in the world, according to the UN. The poverty in the north is in stark contrast to the more developed southern states. While in the oil-rich south-east, the residents of Delta and Akwa Ibom complain that all the wealth they generate flows up the pipeline to Abuja and Lagos.
Nigeria's 160 million people are divided between numerous ethno-linguistic groups and also along religious lines. Broadly, the Hausa-Fulani people based in the north are mostly Muslims. The Yorubas of the south-west are divided between Muslims and Christians, while the Igbos of the south-east and neighbouring groups are mostly Christian or animist. The Middle Belt is home to hundreds of groups with different beliefs, and around Jos there are frequent clashes between Hausa-speaking Muslims and Christian members of the Berom community.
Southern residents tend to have better access to healthcare, as reflected by the greater uptake of vaccines for polio, tuberculosis, tetanus and diphtheria. Some northern groups have in the past boycotted immunisation programmes, saying they are a Western plot to make Muslim women infertile. This led to a recurrence of polio, but the vaccinations have now resumed.
Female literacy is seen as the key to raising living standards for the next generation. For example, a newborn child is far likelier to survive if its mother is well-educated. In Nigeria we see a stark contrast between the mainly Muslim north and the Christian and animist south. In some northern states less than 5% of women can read and write, whereas in some Igbo areas more than 90% are literate.
Nigeria is Africa's biggest oil producer and among the biggest in the world but most of its people subsist on less than $2 a day. The oil is produced in the south-east and some militant groups there want to keep a greater share of the wealth which comes from under their feet. Attacks by militants on oil installations led to a sharp fall in Nigeria's output during the last decade. But in 2010, a government amnesty led thousands of fighters to lay down their weapons.