Babies are terrorists’ newest weapon, Nigerian officials warn.

Female suicide bombers carrying infants set off explosive devices in Madagali on Jan. 13 after they were let through a security checkpoint where they were mistaken for civilians, the BBC reported. The women killed themselves, two babies and four others.

The women — believed to be from the homegrown Islamic extremist group Boko Haram — could signal a horrifying trend of terrorists using infants in order to avoid detection prior to attacks.

Boko Haram — deemed the world’s deadliest terror group by the Institute for Economics and Peace — is already known for using children and young girls as suicide bombers and slaves after kidnapping them.

The militant Islamist group released 21 Chibok school girls on Oct. 13 after holding them captive for over two years.

At least 15,000 people are thought to have been killed by Boko Haram, according to the International Business Times.

The Jan. 13 incident came just two weeks after two teenage girls blew themselves up and injured three civilians at a checkpoint outside Madagali.