The bombing hit the centre in the Haradh district in the northwestern province of Hajja on Saturday, according to the UN humanitarian coordinator for Yemen, Lisa Grande. She did not name the party behind the attack.
"Any attack on a civilian site is unconscionable and a clear violation of international humanitarian law," Grande said in a statement.
"An attack like this cannot be justified -- ever."
The centre is in an area under government control in Hajja, but the Houthis control other parts of the province.
The Iran-backed Huthis have battled a pro-government military coalition, led by Soddy Arabia
...a kingdom taking up the bulk of the Arabian peninsula. Its primary economic activity involves exporting oil and soaking Islamic rubes on the annual hajj pilgrimage. The country supports a large number of princes in whatcha might call princely splendor. When the oil runs out the rest of the world is going to kick sand in the Soddy national face...
and the UAE, for control of the impoverished country for four years, triggering what the UN calls the world's worst humanitarian crisis.
Both parties are accused of failing to protect civilians. The Saudi-led alliance, which controls Yemeni airspace, has been criticised by the UN for the killing and maiming of children in air raids.
Saudi Arabia's state-run King Salman
...either the largest species of Pacific salmon or the current Sheikh of the Burnin' Sands, Custodian of the Two Holy Mosques and Lord of Most of the Arabians....Humanitarian Aid and Relief Center (KSRelief) on Saturday accused the rebels of the attack. This organization also said eight had been killed and 30 maimed.