Yemen's Houthi rebels said Monday they had transferred 64 child soldiers captured during fighting to a rehabilitation centre and planned to release them in two months.

The United Nations Children Fund (UNICEF) said it welcomed the move.

Abdulqader al-Murtadha, the head of the Houthis' prisoners of war committee, told AFP in Sanaa that "these children were captured on the war fronts while fighting (alongside) government troops".

The children would be handed over to the rebel administration's social affairs ministry for a two-month rehabilitation course before their final release, Murtadha said.

Murtadha accused the Yemeni government and the "countries of aggression", a reference to the Saudi-led coalition fighting there since March 2015, of recruiting teenagers and sending then to the frontlines.

A UN source said all the 64 captured combatants are under 18 years of age.

UNICEF representative Sara Beysolow Nyanti wrote on Twitter that "I welcome the release today in Sanaa by the Houthis of 64 children allegedly captured during military operations".

She voiced hope the rebels would sign up to an action plan "to end the recruitment and use of children in the conflict in Yemen".

Tens of thousands of Yemenis have been killed in the past five years during fighting between the Yemeni government backed by the coalition and the Iran-backed Houthis.

The United Nations and many non-governmental groups have repeatedly denounced the recruitment of child soldiers by both the rebels and the government.

In February 2017, the UN High Commission for Human Rights identified some 1,500 child soldiers in Yemen.