Three of the victims were “slaughtered” in Kolofata, a town which borders Nigeria and that has seen a spate of attacks blamed on the jihadists, said a source close to the security services.
A security officer in the region confirmed the information to AFP, and that two people were also abducted.
In a second overnight attack, Boko Haram fighters are believed to have killed one person and injured another in nearby Ashigashiya, also by the Nigerian border, said the security officer.
The jihadists also burned some 60 boxes of grain and motorcycles, he added.
The attacks come after Cameroon and three other west African states launched a major offensive against the jihadist group in Borno state, in north east Nigeria this week.
Cameroon soldiers, along with troops from Chad, Nigeria and Niger, are targeting a Boko Haram faction led by Abubakar Shekau in the Sambisa Forest, and another led by Mamman Nur, on and around Lake Chad.
According to the Nigerian military, scores of jihadists have been killed and hundreds of others have been forced to surrender in recent days.
Boko Haram began its bloody insurgency in Nigeria in 2009, seeking to install an extremist Islamic state in the country.
The militants began cross-border attacks in 2014, and have regularly carried out raids in Cameroon, killing, looting and kidnapping villagers.
Since 2014, Cameroon has been fighting a military campaign against the group, including cross-border operations with Nigerian troops.
But the group is estimated to have killed some 2,000 civilians and soldiers, and abducted more than a thousand people, in the last four years.
Across the region, violence committed by Boko Haram has killed at least 20,000 and displaced more than 2.6 million people.