A warning has been issued after a man hacked into an online chatroom being used by primary school pupils and exposed himself.

Waltham Holy Cross Junior School in Quendon Drive, Waltham Abbey, published a letter on Monday warning parents of the incident which involved young girls from an unidentified local primary school approached by an online character called 'Odin'.

The OoVoo chatroom, which allows up to 12 people to video chat at the same time, was targeted by Odin, who asked the pupils to expose themselves before breaking into the live conversation and flashing them, the letter said.

Headteacher Vicky Rezaie wrote: "Concern that this app is being used by paedophiles has been highlighted in the national press.

"Please talk to your children about the dangers of this app and similar sites.

"I am sorry to contact you with such a matter, however I thought it was important to make you aware of this situation as soon as possible."

Ms Rezaie and the school has refused to reveal any further details about the incident and which school was involved.

An Essex Police spokesman said: “police have received 10 reports of incidents across Essex since December 2014 where children have received inappropriate images and videos via a social media app, OOVOO, on their mobile phones.

“Schools in the relevant areas and social services have been made aware.

“Investigations into these incidents are on-going and anyone with information which could assist police can call 101.

 “Any children or parents with concerns about staying safe online issue can visit the Essex Police website for advice at www.essex.police.uk/safesurfing.”