Three teenage girls have pleaded guilty to the “senseless” killing of a 75-year-old man in a street attack in north London filmed on a mobile phone.

Fredi Rivero, a Bolivian national, was attacked by the teenagers, aged 15, 16 and 17, in Islington on 27 February, and died in hospital the next day.

Rivero, who has been described as a “much-loved family man”, was near a bus stop on Seven Sisters Road when the girls got off a bus and surrounded him. His glasses were stolen, and he was pushed, shoved, kicked and punched while one of the teenagers filmed the incident on her phone.

Police received reports of the attack at 11.25pm and on arrival found Rivero unconscious with a severe head injury and in cardiac arrest.

Officers later recovered CCTV footage of the assault in which the 17-year-old girl could be seen punching Rivero in the head, causing him to fall backwards. .

DI Devan Taylor, from Scotland Yard, said: “Mr Rivero was a much-loved family man who died in a truly tragic incident. I know how much his death has impacted those close to him and the wider community.

“I would like to offer my heartfelt sympathy to Mr Rivero’s family for their loss and express my admiration for the dignity they have shown throughout the investigation. I also wish to thank the members of public who went to Mr Rivero’s aid as he lay injured.

“The young defendants have now accepted they were responsible for the killing of Mr Rivero, in what was a senseless and completely out of the blue attack on a lone, elderly man. The age of the defendants adds to the devastating nature of this incident and they will now have to deal with the enormity of their actions.”

Appearing before the Old Bailey via video link, the teenagers, who cannot be identified because of their ages, pleaded guilty to manslaughter. They will be sentenced by judge Judy Khan KC on 5 September.

The victim’s daughter, ex-wife and cousins were in court for the hearing.

Khan ordered reports and remanded the defendants into custody.