Gunmen in Nigeria on Friday killed seven people in separate attacks and freed all inmates from a local jail, police said.

Suspected members of the Islamist Boko Haram sect attacked a jail in Kumshe town in Borno state, killing two warders and setting free all the prisoners, state police spokesman Samuel Tizhe told AFP, without specifying their number.

Earlier in the day, suspected Boko Haram members threw explosives and fired gunshots during an attack on a police station in Banki, a Borno town bordering Cameroon, Tizhi said.

"The police repelled the attack and 23 suspects were arrested. Nobody was killed or injured in the attack," he said.

Last month, five people, including a customs and an immigration officials, were killed in Banki by suspected members of the sect in a gun attack.

In the eastern state of Taraba, gunmen disguised in military uniforms shot dead five residents near Babban Mutum town, state police spokesman Ibiang Mbaseki told AFP.

No arrests have been made so far, he said.

Boko Haram has carried out scores of attacks in northeastern Nigeria.