Tripoli - Around 36 000 child migrants, including 14 000 who are unaccompanied, need help in Libya, a major transit hub for migrants trying to reach Europe, the UN agencies said on Monday.

Out of about 400 000 migrants in Libya, 9% are children, the UN children's agency Unicef and the International Organisation for Migration said in a joint statement.

The Unicef and the IOM described the number of unaccompanied children among those needing assistance as shocking.

So far this year, nearly 15 000 unaccompanied children have reached Italy after crossing the Mediterranean, they said.

But 400 died trying to make the treacherous journey, and many more were abused, exploited and detained.

In response, the two agencies said they had joined forces and agreed an "action plan" focusing on child protection, education, water, sanitation and health.

"This collaboration will ensure that child rights are put at the heart of all assistance in Libya," a statement said.

In 2018, the IOM aims to repatriate 30 000 migrants as part of a voluntary return programme, including many children, and around 15,000 have been sent back this year.

"We will be able to collectively work to ensure that all children, no matter their status, are able to gain an education, be protected and receive the basic services they deserve," said Abdel-Rahman Ghandour, Unicef special representative in Libya.

Last month, US television network CNN broadcast video footage appearing to show migrants being sold as slaves near the Libyan capital Tripoli.