The number of children forced to flee Boko Haram's insurgency in Nigeria and neighboring countries has reached 1.4 million, the U.N. children agency UNICEF said on Friday, September 18, according to Reuters.

Around 500,000 were displaced in the last five months after a sharp rise in attacks by the Islamist jihadi group, it said.

The militants have been waging a six-year insurrection to establish an Islamist state in the northeast of Nigeria that has killed thousands and displaced 2.1 million people, most of whom are children.

"In northern Nigeria alone, nearly 1.2 million children – over half of them under 5 years old – have been forced to flee their homes. An additional 265,000 children have been uprooted in Cameroon, Chad and Niger," UNICEF said in a statement.

Now heavily splintered, Boko Haram factions have reverted to guerrilla tactics, raiding villages for supplies and bombing soft targets like places of worships, markets and bus stations.

The largest concentration of internally displaced persons (IDPs) and therefore children are in camps or host communities in Borno state capital Maiduguri, the birthplace of the insurgency. While the army has freed the last few towns still under some form of Boko Haram control, IDPs are reluctant to return home.