"The arrested persons are suspected of being involved in the clandestine smuggling of a large number of irregular migrants into and within the European Union," Europe-wide police agency Europol said Wednesday from its headquarters in The Hague.

The smuggling network specialized in bringing in migrants from the Middle East, especially Libya, Iraq and Syria, mainly through Turkey and the western Balkans, Europol added.

"They were often smuggled in inhuman and dangerous conditions, such as in very small hidden compartments in the floors of buses and trucks, in freight trains or in boats," the agency said.

According to police, migrants sometimes died en route, including one incident when 16 drowned in the river Tisza near the Hungarian-Serbian border in 2009.

Organization 'significantly disrupted'

More than 1,200 police searched 117 houses simultaneously, with officials confiscating a large number of mobile phones, laptops, and bank statements, as well as a semi-automatic rifle with a large amount of ammunition and over 176,500 euros ($240,000) in cash.

Police in Croatia, the Czech Republic, France, Germany, Greece, Hungary, Poland, Slovakia, Turkey and Kosovo made the early-morning arrests.

"We significantly disrupted this main organization," said Nicholas Dove, the head of the organized crime unit of the European Union's Rule of Law Mission in Kosovo.

"This is not a cash on delivery business, this is a cash up front business," said Dove. "Some people who were let down ended up in places where they didn't intend to be."

"Then there's the knock-on effect of people being illegally in countries in Western Europe with no status here. How do they exist? They get involved in street crime. This is hugely damaging to human beings but also to society and the economy," added Dove.

Officials said about 20 members of the organization remained unknown, but pledged to track them down as well.

dr/kms (Reuters, AFP)