Two teenage boys have been taken to hospital and a third suffered minor injuries in a stabbing incident in Littlehampton town centre.
Police were called to Terminus Road in the West Sussex seaside town at 2.45pm on Wednesday following a report that three boys had been attacked.
A Sussex Police spokeswoman said that two of the boys had been stabbed while the third had suffered minor injuries which were not stab injuries.
One suspect had been arrested and another was still being sought, she added.
The spokeswoman said: "A teenager has been arrested and police are seeking another after three youths were attacked in Littlehampton.
"Police were called to a report of a stabbing in Terminus Road at 2.45pm on Wednesday (March 28).
"A 17-year-old boy, initially believed to have life-threatening injuries, and a 16-year-old boy, suffered serious injuries from being stabbed and were taken to Royal Sussex County Hospital, Brighton, where they remain at this stage.
"A 16-year-old boy suffered minor injuries, not thought to have been stabbed, and it is believed the five are known to each other.
"The suspect, a 17-year-old boy, has been arrested on suspicion of three counts of grievous bodily harm with intent. He remains in custody.
"Inquiries are continuing to identify the second suspect."
Shop worker Georgia Simmons said: "We heard some people arguing on the benches outside, by the time we ran to the door we saw a boy holding his shoulder, my colleague went outside and was helping another boy who had been stabbed in the stomach area.
"It started with a bigger group of people mainly boys and they weren't in school uniform but I heard the schools closed early today.
"The group seemed to have split as I saw a few people running towards the clock tower, and the rest were outside my work injured.
"They were all attended to by paramedics, one got taken in an ambulance.
"One was covered in blood and had a pulse monitor next to him.
"I feel very shaken up and upset by what had happened today especially as it was in broad daylight on a Wednesday in the busiest part of Littlehampton.
Safeer Ahmad, of PC Garage near to the scene of the incident, said: "Suddenly the kids were making lots of noises, screaming, I came out and saw what had happened and saw that someone was stabbed. The police have blocked off the whole high street."
Another shopworker, who did not want to be named said: "I heard that it was three boys from rival school gangs."