ROME, Jan. 13 (Xinhua) -- Some 25,800 unaccompanied minor migrants reached Italy last year, more than double the figure of 2015, the UN Children's Fund (UNICEF) said on Friday.

The figure represented more than 90 percent of a total of 28,200 children entering the country by sea in 2016, the agency stressed in a statement.

However, according to Italy's Interior Ministry, some 12,360 unaccompanied migrant children were registered in the country in 2015, a drop from the 13,026 recorded the previous year.

"Such figures show an alarming increase in the flow of extremely vulnerable children, who risk their life to get to Europe," UNICEF senior emergency manager Lucio Melandri said.

The majority of children travelling alone to Italy last year were from Eritrea, Egypt, Gambia, and Nigeria, with most of them boys aged between 15 and 17, according to UNICEF. But an increasing number of younger children and girls was detected.

The UN agency appealed to the European governments for granting more protection to those children, especially to girls, who were believed to be particularly exposed to the risk of "sexual exploitation and abuse, including prostitution, at the hands of criminal networks."

Several underage migrant girls interviewed in Italy in Jan. 2017 said they had been forced to be engaged in prostitution while in Libya to pay off the cost of the dangerous crossing of the Mediterranean to the smugglers, according to the UNICEF.

The agency described such high number of unaccompanied children crossing the Mediterranean from North African coasts to Italy as "unprecedented."

In comparison, only 17 percent of child refugees and migrants arrived to Greece by sea in 2016 were unaccompanied, data showed.

"Besides addressing the factors forcing these children to leave their home, and travel alone, it is necessary to develop a comprehensive monitoring and protection system to safeguard them," Melandri said.

Measures alternative to detention should be implemented for minor asylum seekers and migrants, and all of them should always be granted access to education, health service, and other basic services, UNICEF appealed.

Latest data showed Italy remained on the frontline of Europe's migration crisis in 2016.

According to the Interior Ministry, over 180,000 migrants and refugees reached the country last year, a record high compared with 153,600 registered in 2015, and 169,300 in 2014.