Politicians in Nigeria should put a stop to campaign violence ahead of national polls on Saturday, Amnesty International has said.
The rights group says at least 20 people have died in political attacks and clashes over the last two weeks.
Nigerians will be voting over three weekends – first in legislative, then presidential and lastly in state polls.
It is the third time general elections are being held in Nigeria since military rule ended in 1999.
The previous ones – in 2003 and 2007 – were marred by allegations of widespread rigging, voter intimidation and ballot vote snatching.
Security forces were also accused of siding with the ruling People’s Democratic Party (PDP), which has dominated politics since the return to civilian rule.
Nigeria is Africa’s leading oil producer and most populous nation, but more than half of its 160 million citizens live in poverty.
It has also been bedevilled by occasional outbreaks of deadly violence between the country’s numerous ethnic groups over the last 12 years.
Troops deployed
Muhammad Jameel Yushau, of the BBC’s Hausa Service, says the PDP currently has firm control of both the upper and lower chambers of the National Assembly, but Saturday’s elections are expected to be a stern test for the party.
The 74m registered voters will then vote in presidential polls on 9 April – and for local assemblies and the powerful governors of Nigeria’s 36 states the weekend after.
Amnesty International says some of the worst political violence has been in the southern state of Akwa Ibom.
Other clashes have taken place in south-western Ekiti state, Jigawa state and Bauchi state in the north and Bayelsa in the oil-rich Niger Delta, home state to President Goodluck Jonathan.
“We receive consistent reports that politicians, both candidates and those in office, instigate political violence, despite their statements to the contrary,” Tawanda Hondora, Amnesty International’s deputy director for Africa, said in a statement.
This week, tens of thousands of extra security forces have been deployed across the country.
The BBC’s Peter Okwoche in the capital, Abuja, says he has seen rows of new police vehicles lined up outside the police headquarters on the eve of the polls.
Meanwhile, the independent electoral commission has been deploying more than 400,000 staff.
Election material is being taken to polling stations by plane, boat and road.
Poor infrastructure and difficult terrain have caused serious delays in previous polls, with voting material sometimes arriving two to three days after the election.