Pennsylvania: Up to 20 people stabbed at high school

A teenager armed with two knives has gone on a rampage at a high school in the US state of Pennsylvania, injuring 21 students and a security guard.

A suspect, named as Alex Hribal, 16, was arrested at Franklin Regional High School in Murrysville near Pittsburgh, police said. He was later charged with four counts of attempted homicide and 21 counts of assault.

The wounded, some with serious stab wounds to the torso, were as young as 14. Several needed surgery in hospital.

Rajini Vaidyanathan reports.