The children, whose parents are either dead or cannot be traced, left Tunisia's Shousha camp on Sunday.
Mostly from Somalia, Sudan, Ethiopia and Eritrea, the youngsters aged up to 18 were among 90 who arrived alone from Libya in 2011, the UN High Commissioner for Refugees (UNHCR) said.
In total, 39 have now been resettled, mostly to Norway, Sweden, and Denmark.
"As they had formed strong bonds among each other, the departure has been painful for many of them — not least those still awaiting resettlement," said UNHCR spokesman Adrian Edwards.
Some of the children were parentless when they arrived in Libya while others lost or became separated from their parents before entering bordering Tunisia.
"In these particular cases we believe that resettlement is the best option — we have looked into all other possibilities," Edwards said.
"UNHCR and its partners hope that solutions can quickly be found for the unaccompanied children who remain there (at Shousha) — as well as for the other refugees who await solutions."
The agency called on states, and European countries in particular, to offer more resettlement places for refugees on the borders of Egypt and Tunisia and to speed up decisions on current applications.
Shousha is home to more than 3,000 refugees, many of whom arrived following the bloody conflict in Libya which led to the overthrow of Muammar Qaddhafi.