Italian police arrested 29 people Wednesday accused of belonging to a smuggling ring shipping migrants across the Mediterranean from Turkey and Greece and helping them through Italy to northern Europe.

Police in the southern Italian region of Calabria said the investigation, launched in 2018, had uncovered a "criminal group (which) consisted of citizens from the Middle East, mainly of Kurdish-Iraqi origin", split into cells active in Greece, Italy and Turkey.

Italian police worked with Interpol and Europol, as well as police in Turkey, Greece, Belgium, Germany, Sweden, the UK and Morocco, according to Francesco Messina, head of the police's investigative unit for serious crimes.

Migrants paid between €7,000 and €15,000 for the journey, police said in a statement.

They would pay a first part to a cell in Aksaray in central Turkey, which would organise their transfer across the border to Greece from where the migrants would board sailing boats.

The smugglers also took people boat directly from the Turkish coast, often Izmir, across the Mediterranean to the south of Italy.

"Once the migrants neared the Italian coasts, they contacted their associates in the Italian cells, who helped them travel to northern Italy for a fee of about €500 to €600," police said in a statement.

The migrants were taken first to Milan or Turin, and then on to Trieste or Ventimiglia, crossing the border on lorries, trains or taxis, depending on how much they paid.

Those unable to pay for stages of their journeys were stranded or told to contact relatives back home to get the funds needed, police said.

Over 45,000 migrants have landed in Italy so far this year, according to the Italian interior ministry, nearly four times the number than in the same period last year.