Gunmen suspected to belong to a violent robbery gang raided a remote village in northern Nigeria, killing 20 people in an attack highlighting the growing insecurity in the nation, an official said Wednesday.

The assault happened Tuesday morning before dawn in Kabaru, a village near other towns in Zamfara state that were recently attacked by the gang, state spokesman Nuhu Anka said. The gunmen shot dead most of those they found in the village, then later "slaughtered" the local village chief in a brutal machete attack, Anka said.

Police have begun an investigation into the attack, he said. The assault appeared to be the work of a violent gang blamed for several mass casualty attacks in the region in recent months. In June, gunmen killed at least 27 people in Zamfara state in attacks on villages preparing for a local market day. Earlier in October, gunmen armed with assault rifles attacked a rural village in neighboring Kaduna state, killing at least 24 people, including worshippers leaving a mosque after prayers before dawn.

"It looks like the same people because the pattern is the same," Anka said.

Officials said the Kaduna attack likely came after a local vigilante group in the community killed some of the robbers.

While police routinely have many officers stationed throughout major cities in Nigeria, police presence in villages can sometimes be a single officer working out of someone's home.

Meanwhile, Nigeria's Muslim north remains under guerrilla attack from a radical Islamist sect known as Boko Haram, which has killed more than 720 people this year alone, according to an Associated Press count. The death toll has climbed despite an influx of additional soldiers and police.

The violence has embittered many living in the region and exposed the inability of Nigeria's weak central government to provide basic security in the nation of more than 160 million people.