Children as young as one year old have fallen victim to online paedophiles, according to the NSPCC.
There were 3,186 internet-related sex crimes against children recorded by 38 police forces in England and Wales in 2015/16, according to the charity's report.
The offences included sexual assaults, grooming victims and inciting children to take part in sexual acts.
Where a victim's age was provided by police, most were 13 years old but 272 were under the age of 10 and the youngest was just one year old.
Chief executive of the NSPCC Peter Wanless said the figures "confirm our fears that the online world is playing a significant role in the sexual abuse of children in the UK".
He added: "It's clear that a large volume of sexual assaults and rapes of children have involved the use of the internet - for example by grooming victims before abusing them offline, or live-streaming the abuse.
"We know grooming is on the rise because children are increasingly telling our ChildLine service how they are being targeted online.
"Predatory adults posing as children try to meet them or blackmail them into meeting up or performing sexual acts on webcams, which obviously terrifies them and can leave some feeling suicidal."
This is the first year that police are required to separately record sex abuse cases where the internet is used but the NSPCC says that a small number of forces said they either didn't know about - or weren't using - the Home Office scheme.
Anne Longfield, Children's Commissioner for England, said the "concerning" figures were likely to be "just the tip of the iceberg".
She added: "Successful police operations show that online sexual offenders use sophisticated methods to target, trick and groom children, and may target hundreds of children at a time.
"The internet is increasingly integral to children's lives and they need to be educated about the risks, as well as how to report suspicious behaviour.
"The effect of abuse, whether it happens offline or online is devastating and we need to ensure therapy to help them recover from their ordeal is available."