A relative said he had found the burned-out, bullet-ridden SUV containing the remains of his nephew's wife and her four children.

A soldier stands by a charred truck after an attack in October in El Aguaje, Mexico.
A soldier stands by a charred truck after an attack in October in El Aguaje, Mexico. (AP)

Mexico's top security official said on Tuesday that at least three women and six children were killed by cartel gunmen and one child was still missing in northern Mexico. Relatives said the victims are also US citizens.

Security Secretary Alfonso Durazo said the gunmen may have mistaken the group's large SUVs for rival gangs. He said six children were wounded in the attack and five have been transferred to hospitals in Phoenix, Arizona.

Relatives said the victims live in the La Mora religious community in northern Mexico, a decades-old settlement in Sonora state founded as part of an offshoot of The Church of Jesus Christ of Latter-day Saints.

They said the group was attacked while travelling in a convoy of three SUVs. The asked not to be named for fear of reprisals.

The relative said he had located the burned-out, bullet-ridden SUV containing the remains of his nephew's wife and her four children – twin six-month-old babies and two other children aged 8 and 10.

The US Embassy did not immediately respond to requests for comment.

Mexico's federal Department of Security and Citizens' Protection said late on Monday that security forces were reinforced with National Guard, army and state police troops in the area following "the reports about disappearance and aggression against several people."

The troops were searching for the missing community members, believed to include 11 children or more.

Another relative, Julian LeBaron, said on his Facebook page the dead woman was Rhonita Maria LeBaron.

The first relative said a convoy of three vehicles had set out Monday from La Mora, about 112.6 kilometres south of Douglas, Arizona, but was attacked by cartel gunmen in a possible case of mistaken identity by gunmen.

Many of the church's members were born in Mexico and thus have dual citizenship.

While he said he found the first vehicle, the other two SUVs were missing along with their passengers.

Jhon LeBaron, another relative, posted on his Facebook page that his aunt and another woman were dead, which could bring the death toll to at least seven. He also posted that six of his aunt's children had been left abandoned but alive on a roadside.

It would not be the first time that members of the break-away church had been attacked in northern Mexico, where their forebears settled –– often in Chihuahua state –– decades ago.

In 2009, Benjamin LeBaron, an anti-crime activist who was related to those killed in Monday's attack, was murdered in neighbouring Chihuahua state.

Source: AP