By Alex Last
BBC News, Lagos
Millions of Nigerians are being treated like second-class citizens because they cannot prove their roots lie in the area where they live, a report says.
Ethnic and religious disputes often turn deadly
Lobby group Human Rights Watch says state governments regularly deny access to jobs and basic services to people seen as non-indigenous.
This official discrimination helps fuel ethnic and religious conflict, it says.
There are more than 250 ethnic groups in Nigeria. Thousands have been killed in communal clashes since 1999.
As Nigerians have migrated around the country, their origins have become a major social and economic issue.
If a person cannot prove they are descended from the original settlers of the area where they live, they're categorised as "non-indigenes".
It does not matter if their family has lived in the area for more than a century.
HRW says state and local governments regularly deny non-indigenes access to government jobs, academic scholarships, even access to basic services.
An elderly Hausa resident of Zangon-Kataf in southern Kaduna said his family had lived there for 200 years but he still faced harassment and violence.
Their homes were burnt to the ground in 1992.
"Our parents were born here and we ourselves were born here. We know no other place other than here and so we have nowhere else to go," he said.
The author of the report, Chris Albin-Lackey, says the discrimination is often driven by local leaders, seeking to divert blame for their own failings.
"By denying non-indigenes access to certain economic and educational opportunities, they're seeking to curry favour with their indigene constituents," he says.
"At the end of the day it's really a failure of leadership on the part of the federal government that has allowed all of this to happen."
Human Rights Watch says this discrimination helps fuel ethnic and religious violence, as poor communities struggle over control of resources.
Just two weeks ago in central Nigeria, there was a dispute over whether a non-indigene had the right to take sand from a river bed to build a house.
It sparked clashes which left more than 20 people dead.
Human Rights Watch says the federal government must legislate to end the discrimination.
Changing ingrained attitudes on the ground, though, could prove more difficult.
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