After lurching from one military coup to another, Nigeria now has an elected leadership. But the government faces the growing challenge of preventing Africa's most populous country from breaking apart along ethnic and religious lines.
Political liberalisation ushered in by the return to civilian rule in 1999 has been followed by militants from religious and ethnic groups pursuing their demands through violence.
Thousands of people have died over the past few years in communal attacks led by the al-Qaeda ally Boko Haram. Separatist aspirations have also been growing, prompting reminders of the bitter civil war over the breakaway Biafran republic in the late 1960s.
At a glance
- Politics: People's Democratic Party (PDP) has dominated since the return to civilian rule in 1999. The al-Qaeda-aligned Boko Haram armed movement is conducting an insurrection in the mainly Muslim north
- Economy: Nigeria is Africa's leading oil producer; more than half of its people live in poverty
- International: Nigeria plays a prominent role in African affairs; has withdrawn troops from oil-rich Bakassi peninsula to settle border dispute with Cameroon
Country profiles compiled by BBC Monitoring
The imposition of Islamic law in several northern states has embedded divisions and caused thousands of Christians to flee.
The government is striving to boost the economy, which experienced an oil boom in the 1970s and more recently benefited from high prices on the world market. But progress has been undermined by corruption and mismanagement.
The former British colony is one of the world's largest oil producers, but the industry has produced unwanted side effects.
The trade in stolen oil has fuelled violence and corruption in the Niger delta - the home of the industry. Few Nigerians, including those in oil-producing areas, have benefited from the oil wealth.
In 2004, Niger Delta activists demanding a greater share of oil income for locals began a campaign of violence against the oil infrastructure, threatening Nigeria's most important economic lifeline.
Nigeria is keen to attract foreign investment, but is hindered in this quest by security concerns as well as by a shaky infrastructure troubled by power cuts.