Online child abusers are seeking to take advantage of the coronavirus pandemic, international law enforcement agency Europol has warned.
Europol said it had information that “strongly indicates increased online activity by those seeking child abuse material”.
With schools closed and many working from home, children are more likely to be using the internet unsupervised.
The agency also said cyber-criminals are taking advantage of the crisis.
In online forums and boards, child abusers are ”welcoming opportunities to engage with children”, Europol said.
It warned that abusers expect children “to be more vulnerable due to isolation, less supervision and greater online exposure”.
A spokeswoman said the agency could not share which national law enforcement agencies had raised concerns, but described the increase in activity as a “worrying trend”.
“There are lots of kids at home, off school, and they’re online while their parents are busy working,” said Prof Alan Woodward, a cyber-security expert at the University of Surrey.
“Understand the risk - it’s the very time that these people take advantage of your attention being somewhere else.”
The NSPCC said technology companies also had a “vital job” to do in protecting children from abusers on their platforms - and report suspicious activity to police.
“Worryingly, abusers will see this national health emergency as an opportunity to target children who are spending more time online and may be feeling increasingly lonely or anxious because of the lockdown,” said Andy Burrows, NSPCC Head of Child Safety Online.
“At home it is now more important than ever for parents and carers to be having regular conversations with their children about what they’re doing online, and that they know they can come to you with any worries they may have.”
The NSPCC’s Net Aware website contains information for parents about different social networks and websites, and how to stay safe online. It has recently added articles about video chat and livestreaming services, and the newly-popular Netflix Party extension.
Europol’s report also warned of the high level of other cyber-crime, including phishing emails that pretend to contain information about the virus in links and attachments which "aim to profit from the global health concern.”
Many of the scams being employed are classic cyber-attacks, with a new coronavirus angle in the way they are presented.
“The psychology they’re using is the same, but some of the classic human responses are heightened at the moment,” Prof Woodward said.
"Fear, doubt, and uncertainty is a classic one to play on.”