Media playback is unsupported on your device Media caption 'He switched his webcam on and started groaning'

Sex offenders are increasingly using live online streaming platforms to exploit children, police have warned.

Children need to be educated on the risks associated with streaming sites, the National Crime Agency said.

It said offenders were learning how young people communicated online and "using this knowledge to abuse them".

In one week, authorities identified 345 vulnerable children and arrested 192 people, 30% involving streaming, blackmail and grooming.

Online security

Social media channels such as YouTube, Facebook, Instagram and Snapchat all allow some form of live capability, while there are also many pure live streaming services, including Periscope, Omegle, Liveme and Lively.

Police say abusers thrive on the immediacy these live platforms offer - targeting children with tricks, dares and threats to manipulate them into nudity or sexual acts.

They called for help from parents and internet companies to help manage the evolving threat children face online.

Media playback is unsupported on your device Media caption Child Sexual Exploitation lead explains why parents need to be more intrusive online.

National Police Chiefs' Council Lead for Child Protection Chief Constable Simon Bailey said: "We need parents and carers to talk to their children about healthy relationships and staying safe online.

"We need internet companies to help us stop access to sexual abuse images and videos and prevent abuse happening on their platforms."

An NCA survey found that while 84% of the 927 people who responded said they were alert to the potential dangers their children faced online, more than 30% had not spoken to their children about online safety in the last month. Almost 58% were not sure if they had adequate online security.

Analysis

By Angus Crawford, BBC News correspondent

For many parents the world of live streaming apps is a bewildering one. Every month new ones emerge, to become the latest "must do".

At their most basic they allow young people to broadcast live to the world from anywhere - classroom, playground or bedroom. Some only let a limited number of people see the broadcaster, others are open to anyone using the app - and that includes predators.

It's easy to see why children like the apps. It's immediate, it seems like fun and many idolise the vloggers and Youtubers doing the same thing. The more viewers or "likes" the greater the affirmation for the child.

And for tech companies? Video engages people for longer than anything else online and advertisers love that. The more video a platform can boast, the more advertisers it can attract.

The growth of live streaming apps poses a stark question for the tech industry, one underlined by the NCA campaign - when you create an app that allows children to broadcast live to the world and allows the world to talk back - is it really possible to keep them safe?

Read more about Angus’s investigation here.

'Open conversations'

In a bid to raise awareness among children, a short animation - featuring a fictional abuser called Sam - is being launched by the NCA's Child Exploitation and Online Protection Centre (Ceop).

Released alongside the hashtag #WhoIsSam, the clip will show children and young people how offenders attempt to build exploitative virtual relationships.

Zoe Hilton, from the NCA, said: "Offenders will take advantage of the fact that young peoples' inhibitions are lower online so we're also encouraging parents to talk to their children about what a healthy relationship looks like and how to spot when someone might not be who they say they are.

"As well as ensuring that privacy settings are in place on the sites and apps they use, it's so important that we have regular and open conversations with our children about being safe online and encouraging them to speak up if something is worrying them or doesn't feel right."

Updated guidelines have been added to Ceop's Thinkuknow website, providing parents and guardians, and children of all ages with the latest advice on keeping safe online.

Further guidelines have been issued in a report called Digital Childhood which looks at concerns and makes recommendations for specific age groups.

For example, it says parents should supervise their under-fives at all times online and suggests greater efforts should be made to stop 10 to 12-year-olds signing up to social media sites that are for those aged 13 and older.

UK police forces have also increased offline intervention activity, working with schools, universities and after school clubs to increase awareness.