A teenager knifed a 13-year-old schoolboy after a row over Snapchat messages.

The 15-year-old was armed with a lock-back knife when he stabbed his younger victim on the upper leg and left him lying on the ground.

Both teenagers were on their lunch break from separate schools when the attack took place on the southside of Glasgow in March this year.

The attacker, who fled the scene before caught by police soon after, admitting assaulting the boy to his severe injury at the city's Sheriff Court on Friday.

The court heard that the boys got into a disagreement over Snapchat messages sent by the older teen a few days before the stabbing that led the victim to believe he wanted to fight him.

Prosecutor Harry Findlay said: "He attacked him by surprise. The 13-year-old tried to defend himself, but was taken out onto the busy road and oncoming traffic.

"The accused produced a lock-back knife and stabbed him on the upper leg."

A passer-by then helped the boy, who ended up needing surgery for a leg wound.

Sheriff Johanna Johnston QC bailed the attacker, who can't be named for legal reasons, pending sentencing.

She told him: "The upper leg has a major artery running through it and it can be damaged because of that.

"You are well aware of the serious injury you caused and what happened to him following that.

"This was something you wouldn't want to suffer or anyone you knew.

"You are well aware the court has to punish you."