Kenyan youths have begun construction of a security barrier along the vast and porous border neighbouring war-torn Somalia, although critics have scoffed it cannot work, reports said on Thursday.

The proposed barrier is the latest in a string of measures Kenya has announced to stem attacks by Somalia’s Al-Qaeda-linked Shebab insurgents in the wake of a university massacre in the northeastern town of Garissa.

Youths from a government youth training scheme started digging a ditch this week in Kiunga, Kenya’s coastal Lamu district, which officials said would stretch for some 700 kilometres (435 miles).

"The fence will consist of various obstacles including a ditch and a patrol road,” Immigration Services director Gordon Kihalangwa said, according to The Star newspaper.