Gunmen have killed seven Muslim worshippers and injured three others in two separate attacks on mosques in northwest Nigeria's Kaduna state, police said Saturday.

Suspects from criminal gangs -- referred to as bandits -- opened fire Friday on worshippers in Saya-Saya community in Ikara district during evening prayers, killing six people, Kaduna state police spokesman Mansir Hassan said in a statement.

"At about 8:00 p.m. (1900 GMT) on Friday, we received information from Saya-Saya village that six persons were killed while performing last prayer of the day... in a mosque," Hassan said.

"Bandits, about nine of them on motorcycles, arrived and attacked the people in the mosque," he said.

The gunmen then moved to neighbouring Tashar Dauda village where they attacked another mosque, killing one person and injuring three others, he said.

The assailants took four motorcycles before fleeing into the bush, Hassan said in the statement.

Abdulrahman Yusuf, the local chief of Saya-Saya said the head of vigilantes in the village was among the worshippers killed in the mosque.

"We believe he was the main target of the attack and he was from all indications trailed to the mosque by the bandits," said Yusuf who was among worshippers that escaped unhurt.

Kaduna is one of several states in northwest and central Nigeria terrorised by bandits who raid villages, kill and kidnap residents as well as loot and subsequently burn homes.

The criminals, who are motivated by financial gains, periodically attack churches and mosques to kidnap worshippers for ransom or to avenge their comrades killed or arrested by local vigilantes fighting them.

Local authorities in Kaduna have expressed concern over increasing alliance between the bandits and jihadists waging a 14-year insurgency to establish a Caliphate in the northeast.