Police forces across the world are warning that criminals and paedophiles are using the coronavirus lockdown to target children.
Data gathered by the BBC reveals demand for abuse imagery has shot up.
Reports of obscene online material more than doubled globally to more than four million between March and April.
The US-based Center for Missing and Exploited Children said some of that rise related to one especially horrific and widely-circulated video.
In the UK, where 300,000 people are considered a threat to children, there were nearly nine million attempts in the last month to access child sexual abuse websites which had been previously blocked by the Internet Watch Foundation.
The anti-child abuse charity which reports sites to internet service providers, says that since the lockdown began there has been an 89% drop in site deletions by the tech companies.
It believes this may be because many of these firms have fewer people staffing their hotlines during the pandemic.
Spanish National Police say reports of online child sex videos leapt by just over 20% since just before the lockdown there began on 13 March.
Their counterparts in Denmark revealed the number of attempts to access child abuse websites has trebled.
With most schools closed, children are spending more time online. Experts say that puts them at greater risk of grooming for sexual abuse.
Cathal Delaney of Europol told the BBC: "Children are more vulnerable, they're isolated, they're not being as well supervised online and they're spending more time online during this period than they would have previously.
Dark web surge
"Those conditions lend themselves to children being approached in different ways or coerced or exploited."
Demand for abuse imagery has also shot up in Australia, where police say the downloading leapt by 86% in the three weeks after the 21 March lockdown.
Commander Paula Hudson of the Australian Federal Police, said many offenders see the pandemic as an ideal opportunity to target children.
"Across the dark web we've actually identified Covid-19-themed child exploitation forums," said Cdr Hudson.
"One particular one we're monitoring has grown by more than 1,000 members. They're actively discussing the Covid opportunity to find more victims.
"The internet traffic is so heavy that we've been finding that dark web systems are crashing."
Real world abuse
Many child abuse videos commissioned to order by paedophiles are made in the Philippines, where children are trafficked by abuse rings.
The children who are held captive by the gangs are subjected to appalling violence on camera. These attacks are live-streamed to paying customers in western nations, including the UK.
Officials in the Philippines say reports of online abuse material have soared – from approximately 59,000 in February to more than 101,000 in March, the month that the country's coronavirus lockdown began.
The International Justice Mission (IJM), a global organisation that works in the Philippines, says half of the children rescued from abuse gangs are 12 years old or younger – and it has come across two victims who were babies less than three-months-old.
Earlier this month, police in the country intercepted one gang and took three children into care, the youngest of whom was just six.
Detectives suspect they may have been forced to take part in live-streamed abuse videos.
A 34-year-old woman arrested in the operation was the mother of two of the allegedly abused children. This is consistent with IJM research that found two-thirds of abuses are either parents or close relatives of the victims.
Child abusers already face life terms in the Philippines – and some legislators are proposing changing the law to introduce the death penalty.