"IOM is reporting 45 dead among internally displaced persons, 65 injured (and counting)," spokesman Joel Millman told AFP by email, adding that "75 IOM staff are on hand assisting" the victims.
Earlier Doctors Without Borders (MSF) reported at least 15 dead when an air strike hit Al-Mazrak camp in Hajja province.
The UN Office for the Coordination of Humanitarian Affairs (OCHA) also said the camp had been hit.
Arab coalition warplanes, led by Saudi Arabia, have been pounding rebel Huthi positions in Yemen for the past five days.
The manager of the MSF programme in the Middle East, Pablo Marco, said 500 new families had arrived at the camp over the past two days.