By Katy Migiro

NAIROBI (Thomson Reuters Foundation) - Liberia has the highest proportion of children missing out on primary school education, the United Nations said on Thursday, with nearly two-thirds of its children never stepping inside a classroom.

African countries hit by conflict featured prominently in UNICEF's first global out-of-school ranking, with South Sudan coming joint second with Eritrea on the list. In both countries, 59 percent of children are out of school.

Last month UNICEF said a spike in the forced recruitment of child soldiers in South Sudan could be imminent amid fears the East Africa nation was on the brink of renewed civil war.

Although school is vital for children living in crises, education is one of the least funded sectors in humanitarian appeals, the U.N. children's fund, UNICEF, said in a statement.

"For countries affected by conflict, school equips children with the knowledge and skills they need to rebuild their communities once the crisis is over," UNICEF's chief of education Jo Bourne said in the statement.

"Schools can also protect children from the trauma and physical dangers around them."

Classroom routines can help children psychologically after witnessing atrocities, as well as safeguarding them from abuse, experts say.

A crisis fund was launched in May at the World Humanitarian Summit to increase funding for children missing out on school due to war and natural disasters.

The West African country of Liberia, which emerged from two civil wars in 2003, temporarily shut its schools to stop the spread of the Ebola epidemic, which ended in June.

The 18 million children in the 10 worst countries for access to primary school account for almost one third of the world's 61 million primary school-aged children who are out of school, UNICEF said.

Here are the top 10 countries in the world with the highest proportion of children missing out on primary school:

1) Liberia - 62 percent

2) South Sudan - 59 percent

3) Eritrea - 59 percent

4) Afghanistan - 46 percent

5) Sudan - 45 percent

6) Djibouti - 43 percent

7) Equatorial Guinea - 42 percent

8) Niger - 38 percent

9) Mali - 36 percent

10) Nigeria - 34 percent

(Reporting by Katy Migiro; Editing by Katie Nguyen.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women’s rights, trafficking, property rights and climate change. Visit http://news.trust.org to see more stories.)