The governor of Mandera County, Ali Roba, said the security guards had managed to save 27 people during the attack, which happened in the early hours of Thursday morning.
Mr Roba said in a post online: “We have suffered another sad attack.”
He told Reuters news agency: "If not for the quick response by our security forces, we would be talking of many more casualties now."
The government in Kenya issued a terror alert in March and said parts of Mandera were likely to be targeted.