A youth has been found guilty of killing a 16-year-old boy with a “ninja-style” red sword bought online.

The 17-year-old boy, who cannot be named for legal reasons, stabbed Rahaan Ahmed Amin in the chest on July 9 in retribution for an earlier stabbing, jurors heard.

On Friday, the defendant was found guilty of murder and having a blade following a trial at the Old Bailey.

Prosecutor Kate Lumsdon KC had told jurors how the defendant had cycled into West Ham Park in Newham, east London, with his face covered.

He had produced a long red knife and attacked Rahaan before making off.

Rahaan and his attacker were said to be standing “toe-to-toe” before the knife was used, while another witness said he saw a boy coming towards him with his hands over his chest shouting “save me, save me please”.

Paramedics were called to the scene and Rahaan was taken to hospital where he died the next day.

Police recovered the murder weapon bearing the defendant’s fingerprints and the victim’s blood on the blade hanging in a tree in the park.

They also uncovered a Snapchat photograph of nine knives lined up on the defendant’s bed, one of which looked like the red sword used in the killing.

An identical knife had been ordered on the internet through an online shop in the weeks before the killing, on June 12.

Three orders had been made with a passport belonging to the father of one of the defendant’s friends who told police he had no knowledge of the purchase, the court heard.

The last order was made with the defendant’s home as the delivery address.

Jurors were told that the killing came amid tensions between the defendant and victim’s groups of friends.

When one of the defendant’s friends was stabbed, Rahaan had been arrested on suspicion of involvement.

Snapchat messages suggested the defendant and his friends wanted to harm Rahaan in retaliation, the court was told.

Giving evidence in his trial, the defendant claimed he used the knife in self-defence.

Sentencing was adjourned until September 6 for reports to be prepared.