At least 12 people have been kidnapped in two separate incidents in northern Nigeria, officials and witnesses said on Saturday.

In the first incident, unidentified assailants kidnapped four people late on Friday. Those taken included the village head of Nasarawa-Burkullu community in northwestern Zamfara state, local official Muhammad Bukuyum said on Saturday.

Bukuyum said the other victims were three local farmers, and that the assailants had demanded a ransom, without giving further details.

In a separate incident, Boko Haram militants abducted eight farmers on Saturday in Maiwa village, about three kilometres from Maiduguri, the capital of northeastern Borno state.

Mohammed Jida, who managed to flee from the attackers, told Reuters he sighted the insurgents surrounding the farmers as they worked on their farm.

"As I sighted them, I started running with others, scampering for safety. Luckily, I managed to escape but the rest of my colleagues were caught by Boko Haram."

Greema Abubar and Bukar Kachallah, who are relatives of some of the victims, confirmed the attack, adding that the insurgents had demanded a ransom, without giving further details.

Borno police spokesman Sani Kamilu Shatambaya did not immediately respond to calls for comment.

Armed gangs, often referred to locally as bandits, have wreaked havoc across northwest Nigeria in recent years, kidnapping thousands of people, killing hundreds and making it unsafe to travel by road or to farm in some areas.

On Friday, Boko Haram freed 49 women kidnapped earlier in the week near Maiduguri after a state official paid a ransom for their release.

The Islamist group has been killing and abducting farmers in Borno state, a hotbed for militancy that has been the epicentre of a 14-year war on insurgency in Nigeria.

Reuters