Five schoolchildren aged between 13 and 15 have been arrested on suspicion of robbery and assault at the city centre.
At around 1pm on Tuesday a girl aged 15 was the victim of an assault by two girls outside the Point.
Then around 8pm on Wednesday a 14-year-old boy was assaulted and had property stolen.
Police have now arrested a 14-year-old girl, a 15-year-old girl, a 13-year-old boy and a 14-year-old boy on suspicion of robbery and assault without injury in connection with the incidents.
A 14-year-old girl was also arrested on suspicion of assault without injury in connection with the incidents.
All five currently remain in police custody.
Detective Sergeant Andy Pearce said: “I would like to hear from anyone who has any details which could assist the investigation. If anyone in the local area has any concerns or information please speak to an officer or call the 24-hour non-emergency number 101.”
Anybody information should quote reference 43180032353 when they call 101. Or they contact Crimestoppers anonymously on 0800 555 111.