GENEVA (Reuters) - Slightly fewer than half as many migrants reached Europe by sea in 2017 than 2016, the International Organization for Migration (IOM) said on Friday, with curbs finally cutting traffic on the deadly route from Libya to Italy.

A migrant waits on the MV Aquarius, a search and rescue ship run in partnership between SOS Mediterranee and Medecins Sans Frontieres, after it arrived in Pozzallo on the island of Sicily, Italy, December 18, 2017. REUTERS/Darrin Zammit Lupi

Two years after more than a million people entered the EU, mostly fleeing war in the Middle East and poverty in Africa, the IOM recorded 171,635 arrivals by boat in 2017. The 2016 figure was 363,504.

The biggest influx of refugees and migrants in Europe since World War Two caused a political and humanitarian crisis two years ago.

Since then, the main Eastern Mediterranean route between Turkey and Greece has largely been shut by a deal between the EU and Ankara.

Reducing traffic has been slower on the other main route, across the central Mediterranean from North Africa to Italy, where thousands of people have died at sea. But numbers finally started coming down sharply in the second half of last year.

Arrivals by boat in Italy accounted for most of the 2017 arrivals: 119,310 in total, down by a third compared to the previous year, the Italian Interior Ministry said on Dec 31.

“We can tell you with confidence that the numbers from North Africa to Italy this year are under 120,000...That’s the lowest in the last four years for arrivals in Italy,” IOM spokesman Joel Millman told a news briefing.

“The same can be said for the arrivals in Greece with 29,595 for 2017, absolutely the lowest in the four years we have been keeping numbers on Greece,” he said. In 2016, some 173,614 migrants arrived by sea in Greece, according to IOM figures.

Some 21,663 migrants arrived in Spain as of Dec. 28 last year, while 1,067 landed in Cyprus, preliminary figures show.

More patrols and rescues off the coast of Libya, as well as fighting between smuggling groups, contributed to the overall drop, Millman said.

The number of migrant deaths at sea has not been finalised, but stands at 3,116, compared to 5,143 recorded in 2016, Millman said.

“We think of those as extremely positive developments,” he said.

African migrants in Libya continue to depart for Europe from the coast, where the IOM is monitoring rescues, he said, adding: “Boats are still rescuing in the hundreds every day, depending on the day, sub-Saharan Africans who have come through Libya.”

Nearly 20,000 Africans went home last year under IOM’s voluntary repatriation program from Libya, including 7,000 since an African Union - European Union agreement reached in Abidjan on Nov. 29, Millman said.

The United Nations agency aims to repatriate a further 15,000 migrants from Libya by the end of January, he told Reuters.