Seven children and an adult were kidnapped from an orphanage by unknown criminals outside Nigeria's capital Abuja, police said Monday.

Aged between nine and 14, the children from the orphanage in Abaji "were plucked away between 1 am and 2 am on Saturday by a group of about 25 men," Rachel Alaje, owner of Rachel's Home For Orphans And Vulnerable Children, told AFP by text message.

Africa's most populous country has been plagued by kidnappings for years, with criminals largely targeting the wealthy and prominent.

But more recently, the pool of victims has expanded and the vulnerable and poor across the country are now also taken for ransom.

Police spokeswoman Mariam Yusuf confirmed the incident and said police had launched a "strategic operation to ensure the children's safe rescue."

Eleven people in total were initially kidnapped, said Alaje, but an adult and two children were released by the criminals and taken back to the orphanage, "because one child was crying and the other one couldn't walk."

Alaje said she received a request to pay 10 million naira ($26,000) for the release of the orphans.

A 2020 report by SB Morgen, a Nigerian geopolitical consulting firm, concluded that over $18 million (nearly 15 million euros) had been paid in ransoms since 2011.

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