A man has been stabbed 'by a man in a balaclava' during an early morning jog in Morden.

Officers say the 20-year-old was out for a run at 5am in Morden Hall Park on June 29 when he was approached from behind.

A man - described as black, 5ft 7ins and dressed in dark clothes, gloves and a balaclava - stabbed the victim in the side, according to police.

He did not say anything during the encounter and escaped using the park entrance near Phipps Bridge Road.

The man suffered serious internal injuries and required surgery.

Police want to identify a potential witness, described as a man of 'black African appearance' who shouted over to the victim and three other men who helped the victim after the attack.

Three men arrested in connection with the stabbing have been released without charge. The motive of the crime is unknown.

Anyone who has information is asked to contact the police on 101 or via Crimestoppers on 0800 555 111.