"Tens of thousands of people have fled their homes, some by crossing the sea to Djibouti and Somalia," UN Under-Secretary General for Humanitarian Affairs Valerie Amos said, according to AP.
She added that "all sides must avoid targeting hospitals, schools, refugee camps and civilian infrastructure, particularly in civilian areas," while the UN was "working with local authorities to provide emergency health kits and generators."
The agency said in its report that more than half of the 25 million people in the country already live in poverty, while there are 330,000 refugees from previous conflicts.
"It is a terrible situation and it is moving so fast. We are heading toward a humanitarian disaster," said Harneis, the Yemen representative of the United Nations Children Fund.
Harneis said that "62 children were killed in the first four days of the operation as many as were killed in all of 2014, when the Houthis were fighting to expand their hold. Some of the children were bystanders, and some were used as child soldiers," according to AP.
He estimated that about a third of the fighters on all sides are under the age of 18.
Last week Saudi Arabia, with the support of Bahrain, Qatar, Kuwait, and the UAE, launched air strikes to back President Abed Rabbo Mansour Hadi and his loyalists against Shiite rebels known as Houthis and their allies.
Egypt, Jordan, Morocco, Pakistan and Sudan later joined the operation.
