KADUNA, Nigeria - At least 20 Muslim worshippers were killed by unknown gunmen at a mosque in Nigeria's northern state of Kaduna on Sunday morning, local police sources have reported.

The fresh raid was located in the village of Dogon Dawa in the Birnin Gwari local government area of the state, the sources said, adding that most of the victims were settlers in the remote area.

"The gunmen carried out the attack after embarking on a house to house search, shooting and killing people indiscriminately. Some of the victims were also stabbed to death by the attackers," said a police officer, who preferred anonymity. ?

Spokesperson of the National Emergency Management Agency Yushau Shuaib also confirmed the shooting incident by marauders, but could not ascertain the casualty figures.

The police are "in the right position to give details about the gunmen attack. We are not sure if the attack was orchestrated by any group or mere armed robbers. The police will make that known to the public when they finish with investigation," he explained.

However, some villagers in the Dogon Dawa community claimed that the attack was perpetrated by a group of armed robbers who had earlier warned of impending assault after their hideouts were revealed to security operatives, following a recent raid by the bandits.

"The gunmen who were armed to the teeth seem to be on a revenge mission," said a source who also preferred anonymity for security reasons.

Another source told Xinhua that residents of the community have started fleeing the area following the morning attack.

So far, the police have declined to make official statements on the attack, but highly-placed officials told Xinhua that the media will be addressed later on the shooting incident.

Nigeria's northern part has been plagued by violence in recent years, with frequent reports of shooting and bomb attacks, mostly claimed by the Boko Haram sect.

The most recent of the attacks occurred on Thursday, when at least 14 people were killed in separate attacks by gunmen in Jos, capital of Plateau State, in central Nigeria, according to military authorities.

At least 815 persons have been killed in attacks by Boko Haram in Nigeria this year, the Human Rights Watch said in its latest report in October.

Hundreds of attacks by the sect have left more than 1,500 people dead since Boko Haram staged an uprising in the northern city of Maiduguri in 2009, according to the report.