Nigeria, Jan. 23 -- Fear is now mounting that Borno State may soon be totally cut off from the rest of Nigeria as Boko Haram insurgents in the past few weeks have launched daily attacks on the Kano-Maiduguri highway, the only remaining safe route to the state.

Six highways link Maiduguri, the state capital, with other parts of Nigeria. But for the past six years, only the Kano-Maiduguri highway that connects the state with Damaturu, the Yobe state capital, remains in use.

Between 2013 and late 2014, the insurgents bombed major bridges on four of the highways, rendering the roads inaccessible. They also seized many communities along the highways.

Today, to travel from Maiduguri to Biu, about 180 kilometres in the southern part of the st...