A couple were "brutally attacked" in front of their children as they enjoyed an afternoon in the sunshine, police say.
The parents, a man, 30, and a woman, 26, needed treatment for serious head and back injuries following the shocking assault.
Groups of teenagers were nearby and officers are keen to trace two girls - thought to be aged as young as 12.
The victims were rushed to hospital after the attack on a canal path in Drumchapel, Glasgow, at just after 5pm on Saturday.
Police also want to speak to a boy aged between 13 and 17 in connection with the incident.
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Older teenagers are thought to have been drinking nearby and officers are monitoring "continued" anti-social behaviour in the area.
The boy is described as aged 13 to 17 with brown hair and was wearing a bright yellow T-shirt and dark jogging bottoms.
Both girls are described as aged 12 to 15.
One had long, dark hair in a ponytail and was wearing a dark T-shirt and black Adidas joggers with three stripes down the outside leg.
The other girl had long blonde hair in a ponytail and was wearing a dark top, denim shorts or a short skirt, and white trainers.
Detective Inspector Kenny McDonald, of Police Scotland, said the parents were "brutally attacked".
"This family were enjoying an afternoon in the sunshine when the parents were brutally attacked and we are keen to speak to anyone with information that can help our investigation," he said.
"We know there were groups of younger teenagers around at the time, as well as older youths, some of whom may have been drinking.
"It is important that we speak to those who were there as they may have information that can assist our enquiries.
"There is also continued anti-social behaviour in this area and officers are carrying out patrols.
"We will not tolerate this kind of behaviour and work towards bringing those responsible to justice and make our communities safer places."