Spanish police said Tuesday they have broken up a human trafficking ring that smuggled desperate families fleeing the conflict in Syria into Europe, charging up to 10,000 euros ($12,500) per person.

Eighteen people were arrested in Madrid, including the suspected head of the ring, a Spanish national of Lebanese origin, police said in a statement.

"The organisation mainly recruited Syrians who were displaced due to the situation in their country. In general it selected middle class families," the statement said.

The ring charged between 6,000 euros and 10,000 euros ($7,500 and $12,500) per person, police said.

"In exchange for this money they had the right to plane tickets, accommodation in the various transit nations, falsified documents and several opportunities to attempt an entry in case they were detected before arriving in Spain," the statement added.

The ring would usually take the Syrians to Asia and then a city in South America, most often in Brazil, before flying them to Madrid from where they travelled overland by bus or tax to France or Germany or another northern European country in a trip that could last weeks.

The Syrians stayed in budget hotels in the centre of the Spanish capital which, in cooperation with the ring, did not register their stay.

Police said they opened their investigation in April after detecting the "suspicious" entry of various Syrian nationals at Madrid's airport.

The suspects include eight Lebanese nationals, three Syrians, a Moroccan, Ecuadorian, a Ukrainian and four Spanish nationals, two of them of Lebanese origin.

Nearly half of Syria's pre-war population of 23 million people has been forced to flee since the conflict in the country began in March 2011 as an uprising against President Bashar Assad.

The United Nations says 3.2 million people have fled beyond Syria's borders, mostly to Turkey, Lebanon, Jordan and Iraq, and more than 7.2 million have become internally displaced. More than 200,000 people have been killed in the war, according to the United Nations.