Europe has a hidden labor market in which migrants and even children are working in "slave-like" situations, a European Union official said Tuesday.

Morten Kjaerum, director of the European Union Agency for Fundamental Rights, warned that the current global economic crisis could push more people into this underground economy and expose them to severe exploitation.

Kjaerum said there is a growing illicit market in Europe "where migrant workers and children are working in what you could say (are) slave-like situations."

Kjaerum, in an interview with The Associated Press, said the problem persists throughout Europe and involves both undocumented foreign nationals and EU citizens.

"The whole issue of ... the "slave-like" labor market is something we have to address again more forcefully," he said.

While the market's magnitude was "very difficult" to assess, such low-end jobs can be found in the sex and farming industries, among others, Kjaerum said. Sometimes, domestic workers also fall into this category.

Reports suggesting the existence of an underground economy within the EU are not uncommon. In late 2006, for example, Polish police said they had arrested the alleged ringleader of a human trafficking network that had shipped hundreds of Poles to what authorities described as virtual slave labor in Italian fruit plantations since 2000.

Sometimes, Kjaerum said, workers in the illicit market even face death.

"We have seen cases in member states where, most likely, these people were shot, killed afterwards just to get rid of them — so it is a real issue," Kjaerum said. He declined to provide more details.

The Vienna-based agency is slated to release a report on child trafficking early next year. According to Kjaerum, very preliminary findings show that the problem is "very much an issue" to which EU nations and institutions need to pay more attention.

Each year, "hundreds, if not thousands" of children come to Europe and simply disappear within days or weeks, he said.

"Some of them we never hear about, others present themselves at the borders as asylum seekers or in other ways and are being transferred to asylum camps or other care centers and then simply disappear."

Kjaerum said it was "most likely" that many of the children either disappear into the sex market, become domestic workers or laborers in industries such as farming.

The European Union Agency for Fundamental Rights was established last year and is meant to advise the EU and its member states as they implement EU laws to ensure that fundamental human rights are observed.