The EU police agency Europol on Sunday said more than 10,000 unaccompanied refugee children have disappeared in Europe, adding that it fears many of them might have become victims of sex trafficking rings.
Europol confirmed to Agence France Presse the figures published in British newspaper The Observer.
The agency's chief of staff Brian Donald told the newspaper that the numbers apply to children who disappeared from the system after being registered following their arrival in Europe.
"It’s not unreasonable to say that we’re looking at 10,000-plus children," Donald said, adding that 5,000 had disappeared in Italy alone.
"Not all of them will be criminally exploited; some might have been passed on to family members. We just don’t know where they are, what they’re doing or whom they are with."
Over one million refugees fleeing from war and poverty have reached Europe in 2015.
Europol estimates that 27 percent of them are children, the Observer said.
"Whether they are registered or not, we’re talking about 270,000 children," Donald told the paper.
"Not all of those are unaccompanied, but we also have evidence that a large proportion might be."
The unaccompanied minors come from various countries - mainly from Syria, Afghanistan, Somalia and Eritrea.
According to UNICEF, approximately 106,000 children applied for asylum in Europe in the first half of 2015, up nearly 74 percent from the same period the previous year.
The vast majority of them are boys aged between 13-17. Currently around 30,000 unaccompanied minors are living in Germany alone.