[Migrant children look on as a bulldozer removes tents from the train tracks during a police operation at a migrant camp at the border between Greece and Macedonia, near the village of Idomeni]More than nine out of ten refugee and migrant children arriving in Europe through Italy this year are travelling 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.