The “traumatic incident” took place at the fishing lake at around 6.50pm on Tuesday, April 25.
Police are appealing for information and witnesses.
The pair were running in the park when a German Shepherd approached and bit them.
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It was reported that the dog’s owner(s) tried to control it, but struggled to do so as it was not on a lead.
PC Lee Rowson, who is investigating, said: “Thankfully the bites did not draw blood, but this was understandably a traumatic incident.
“I am therefore appealing for anyone who might have information about the owner(s) or saw what happened.
“The owner(s) appeared to be two males who were fishing and had a tent with them. One was described as a white male with a beard, and he was dressed in green with a beanie hat on.
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“If you can help, please get in touch by emailing me at [email protected].”
You can report information online at herts.police.uk/report, speak to an operator via online web chat at herts.police.uk/contact or call the non-emergency number 101, quoting crime reference 41/33463/23.
You can stay anonymous by contacting Crimestoppers on 0800 555 111 or via crimestoppers-uk.org.