A trio of runners have been injured after stones were thrown at them in two separate attacks during a weekly 5K run in the city.
Both incidents happened during the Sloughbottom parkrun in Drayton Road.
The first took place on November 5 when a man was hit in the head and a 12-year-old girl was hit in the leg at around 9.40am.
The second took place a week later on November 12 when a woman was struck on the arm by an object while running along Marriott’s Way at around 9.25am, according to a Norfolk Police spokeswoman.
They added there were reports of "youths throwing stones" during the first incident, also in Marriot's Way.
Miranda Ellis, co-event director at Sloughbottom parkrun, said: "I’m concerned.
"These unprovoked attacks are potentially very dangerous.
"We come together as runners, walkers, joggers and volunteers to enjoy exercising together at parkrun, which is a wonderful community.
"We all deserve to be able to enjoy taking part in safety."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here