Two heartless teenage thieves are suspected of stealing from a man fighting for his life after collapsing in Streatham Hill.

A witness spied the two youths, aged about 15, rummaging through the man's pockets at 10.45pm on Thursday evening.

The man had collapsed in Streatleigh Parade due to a pre-existing medical condition when the youths were spied standing over his body, then running from the scene.

The man - who has since been released from hospital after being in a critical condition - is still unable to remember the incident or if anything was actually stolen, leaving police with few leads.

The man's head injuries, described by officers at the scene as "life-threatening", were so serious it was first presumed he had been the victim of a violent robbery.

The incident comes as other examples of teenage criminality emerge this week.

A gang of teenage burglars as young as 14 have been targeting homes in Gipsy Hill and Knight's Hill, while a teenage gang of muggers were also targeting other youths for mobile phones and other personal items in Streatham on Saturday.

Detective Chief Inspector Nick Sedgemore said there had been a noticeable trend of young teenagers, who previously would have been involved in street robberies or "muggings", moving on to break-ins.

He said: "We have seen a real flip for street gang kids to get in to burglary."

The young teenagers are kicking down doors and targeting portable items like i-pods, handheld computer consoles and laptops which could be turned into cash by selling to people their own age.

On Monday a 15-year-old teenager, already electronically tagged as a condition of bail for a previous alleged offence, was charged by police with a burglary in Riggingdale Road, Streatham, where £300 in cash, a bike, an ipod, eight camera lenses and a mobile phone worth more than £1,500 were stolen.

D Chief Insp Sedgemore said it was thought the kids were not linked to larger criminal gangs, and many if caught worked with the Safer Lambeth Partnership's Young and Safe programme young to stop them reoffending.

He urged residents and their landlords to fix secure locks to stop the "chance" burglaries.

He said: "We have reports of groups going from door to door kicking them to see if they will come open."

He said if a door was secure they would generally move on.

He urged people not to attract muggers by having their personal property "on show".

He said people would have a better chance of having stolen electronic property returned by making a note of the equipment's IMEI number, and marking it with a post code and phone number.