Youths targeted two people in apparently random violent attacks at a nature reserve in Motherwell.
The sickening assaults were on a man and a woman in separate incidents on the same evening.
Police now want to trace youths who were part of a gang congregated at the Baron's Haugh nature reserve near the town's historic Dalzell Estate on Monday night.
It is thought at least one of those attacked was running to keep fit.
Motherwell Athletics Club said on its Facebook page: "Serious Incident at Baron's Haugh Nature Reserve.
"We have been informed by one of our athletes that there was a serious incident in Baron's Haugh Nature Reserve on Monday evening.
"A lone female runner was attacked and assaulted by a group of youths. "The police are investigating the incident. Be careful."
The post attracted a string of replies.
One said: "Hopefully the lady concerned is ok and the police catch the culprits."
Another said: "That’s absolutely shocking hope she will be ok. Please if anyone knows something come forward these little cowards need caught!!!"
Police say neither of the victims were seriously hurt and that "enquiries are ongoing".
The Record has previously reported on concerns about vandalism and anti-social behaviour at the reserve.
It is a popular destination for bird watchers and school parties.
Constable Craig Armstrong at Motherwell said: "We are currently carrying out enquiries into two separate assaults, one on a woman and the other on a man, who were passing through the reserve.
"I would urge anyone who may have been in the Baron's Haugh area on Monday evening to get in touch with us if they saw or heard anything which might help us in this investigation.
"Callers can use the 101 number and should quote incident 2973 of 20 July. Anyone wishing to pass on any information and remain anonymous can do so through Crimestoppers on 0800 555 111."
