Time for play: A teacher and her pupils in the yard of a school set up for displaced children
A teacher and her pupils in the yard of a school set up for displaced children. (Representative image) AFP

Dozens of children were abducted by gunmen from a farm in northern Katsina state and the kidnappers were demanding a ransom for their release, police and residents said on Wednesday.

Katsina is the home state of President Muhammadu Buhari and is among states in northwestern and north central Nigeria where armed gangs on motorbikes have killed people or kidnapped them for ransom from villages and highways.

Police spokesman for Katsina Gambo Isah confirmed the abduction of the children but did not give details.

Residents told Reuters that the children were taken on Sunday while harvesting crops at a farm located between Kamfanin Mailafiya and Kurmin Doka villages in Katsina.

A resident whose son was among those kidnapped said 30 children were abducted but that at least two escaped while another one was released because she was sick.

"Only four of the children are boys, the rest are girls aged below fourteen (years)," said the resident, who declined to be named for safety reasons.

A village head from the area said the gunmen were demanding 30 million naira ($68,435) as ransom. Police records showed that at least 22 children were missing.

The use of underage children as farm labourers is common in some states in northern Nigeria, which has the highest number of children out of school in the country, according to the United Nations Educational, Scientific and Cultural Organization.

The military has been bombing suspected hideouts of the gunmen, known locally as bandits, as the government seeks to end the attacks that have raised concerns ahead of a general election next February to choose Buhari's successor.