LONDON (Thomson Reuters Foundation) - More than nine out of ten refugee and migrant children arriving in Europe through Italy this year are traveling alone, the U.N. children's agency UNICEF said on Tuesday, warning of "appalling" risks children face while escaping conflict and poverty.

In the first five months of 2016, more than 7,000 unaccompanied children made the crossing from North Africa to Italy, following a route that in recent weeks has become the busiest and the deadliest for migrants to Europe, UNICEF said.

The children rely on human smugglers, often under a "pay as you go system", making them prone to exploitation and abuse including rape, forced labor, beatings and death, UNICEF said.

It said Italian social workers told the agency some boys and girls were sexually assaulted and forced into prostitution in Libya, while some of the girls arriving in Italy were pregnant as a result of rape.

"If you try to run they shoot you and you die. If you stop working, they beat you. It was just like the slave trade," 16-year old Aimamo told UNICEF.

"Once I was just resting for five minutes, and a man beat me with a cane. After working, they lock you inside," he said, describing conditions on the farm in Libya where he worked for two months with his brother to pay the smugglers.

The number of unaccompanied children traveling from North Africa to Italy so far in 2016 was more than double that of the same period in 2015, UNICEF said, adding that it could not pinpoint one reason why the numbers had spiked.

Christopher Tidey, a UNICEF spokesman, said girls from Nigeria told him they fled to Europe to escape early marriage, while a boy from Somalia said his family sent him away after militant group al Shabaab threatened to recruit him.

"Extreme poverty is a major motivator as well," Tidey told the Thomson Reuters Foundation by phone from Germany.

"I met a number of boys from countries like Gambia who made the trip basically because their families were so poor that the older ones were being sent to Europe effectively to try and earn money to send back home."

As calmer summer weather begins, European officials who struck a deal with Turkey to block crossings to Greece have been scrambling for ways to shut down flows on the other major sea route into the EU from Libya.

Between Jan. 1 and June 5 this year, more than 2,800 deaths were recorded in the whole of the Mediterranean, the vast majority on the dangerous central Mediterranean route from North Africa, compared with 3,770 in 2015, said UNICEF.

It said 235,000 migrants were currently in Libya, tens of thousands of them lone children, many trying to make it to Northern France in hope of eventually reaching Britain.

(Reporting by Magdalena Mis; Editing by Ros Russell; Please credit Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women’s rights, corruption and climate change. Visit news.trust.org)