Police asked schoolchildren to avoid Croydon town centre after reports two rival groups of pupils were planning to meet to brawl.

Officers have written to secondary schools across the borough requesting them to warn pupils of a "heavy police presence" in the area this evening amid "tensions" between youths.

Two teenage boys were knifed during a fight near West Croydon station on Friday night.

It is understood several schools in Croydon were contacted by police, who asked pupils avoid the town centre on their way home after classes.

A large number of police officers were in North End at about 4pm today and there were unconfirmed reports of arrests.

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A letter sent to parents of pupils at St Andrew's Church of England High School yesterday read: "Please be aware that the police have requested that all young people of school age avoid Croydon Town Centre on their way home for the rest of this week, unless absolutely necessary.

"There will be a heavy police presence in Croydon and they will be using CCTV to identify students in town as a result.

"The town centre is a place to avoid whilst tension exists."

The Metropolitan Police said the operation was not linked to Friday's stabbings. No arrests have been made following that violence, which led to two boys being taken to hospital.

One parent told the Croydon Guardian she had heard reports of an effective "turf war" between students from different Croydon schools who congregate in the town centre after school.

The mother, whose daughter attends St Andrew's, said: "I have told her to come straight home after school. It is ludicrous what some of these children are doing to each other these days."

Kerry Targett, headteacher at St Andrew's, said: "We received information from the local police which gave the indication that they didn't want students in Croydon town, so we issued to our students exactly what the police told us: that they were going to have a high police presence and have requested that school students did not go that way home and didn't hang around on the way home if they needed to get buses.

"I've not received anything to say that our students are down there or there are any particular problems. We've got our local police coming in on Monday so I was going to ask what is going on that we might need to be sharing."

She added: "There are a number of schools that meet down there just by nature of how they cross over to get trams."

A police spokesman said "This was in relation to intelligence that we received which stated that two specific schools' pupils were going to have a fight in the Town Centre.

"The respective schools took pro-active action and we increased officers in the town centre that afternoon..

"It is not a comment that we consider the Town Centre is unsafe, it was a response to specific intelligence."

Croydon Council said it was not aware of increased police activity in the town centre.